chore: fix compilation warning

[maksymar]

This PR fixes default-features is ignored compilation warning.

Before log

+ canbench --less-verbose --hide-results --show-summary --csv
~/work/stable-structures/stable-structures/benchmarks/vec ~/work/stable-structures/stable-structures
warning: /home/runner/work/stable-structures/stable-structures/Cargo.toml: `default-features` is ignored for ic_principal, since `default-features` was not specified for `workspace.dependencies.ic_principal`, this could become a hard error in the future
    Finished `release` profile [optimized] target(s) in 0.04s
+ cp ./canbench_results.csv /tmp/canbench_results_vec.csv

After log:

~/work/stable-structures/stable-structures/benchmarks/vec ~/work/stable-structures/stable-structures
+ canbench --less-verbose --hide-results --show-summary --csv
    Finished `release` profile [optimized] target(s) in 0.04s
+ cp ./canbench_results.csv /tmp/canbench_results_vec.csv

[github-actions]

canbench 🏋 (dir: ./benchmarks/compare) 044012a 2025-06-02 09:48:54 UTC

✅ ./benchmarks/compare/canbench_results.yml is up to date
📦 canbench_results_compare.csv available in artifacts

---------------------------------------------------

Summary:
  instructions:
    status:   No significant changes detected 👍
    counts:   [total 18 | new 0 | improved 0 | regressed 0 | unchanged 18]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes detected 👍
    counts:   [total 18 | new 0 | improved 0 | regressed 0 | unchanged 18]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes detected 👍
    counts:   [total 18 | new 0 | improved 0 | regressed 0 | unchanged 18]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

[github-actions]

canbench 🏋 (dir: ./benchmarks/vec) 044012a 2025-06-02 09:48:01 UTC

✅ ./benchmarks/vec/canbench_results.yml is up to date
📦 canbench_results_vec.csv available in artifacts

---------------------------------------------------

Summary:
  instructions:
    status:   No significant changes detected 👍
    counts:   [total 16 | new 0 | improved 0 | regressed 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes detected 👍
    counts:   [total 16 | new 0 | improved 0 | regressed 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes detected 👍
    counts:   [total 16 | new 0 | improved 0 | regressed 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

[github-actions]

canbench 🏋 (dir: ./benchmarks/memory_manager) 044012a 2025-06-02 09:47:57 UTC

✅ ./benchmarks/memory_manager/canbench_results.yml is up to date
📦 canbench_results_memory-manager.csv available in artifacts

---------------------------------------------------

Summary:
  instructions:
    status:   No significant changes detected 👍
    counts:   [total 3 | new 0 | improved 0 | regressed 0 | unchanged 3]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes detected 👍
    counts:   [total 3 | new 0 | improved 0 | regressed 0 | unchanged 3]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes detected 👍
    counts:   [total 3 | new 0 | improved 0 | regressed 0 | unchanged 3]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

[github-actions]

canbench 🏋 (dir: ./benchmarks/btreemap) 044012a 2025-06-02 09:50:01 UTC

✅ ./benchmarks/btreemap/canbench_results.yml is up to date
📦 canbench_results_btreemap.csv available in artifacts

---------------------------------------------------

Summary:
  instructions:
    status:   No significant changes detected 👍
    counts:   [total 285 | new 0 | improved 0 | regressed 0 | unchanged 285]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes detected 👍
    counts:   [total 285 | new 0 | improved 0 | regressed 0 | unchanged 285]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes detected 👍
    counts:   [total 285 | new 0 | improved 0 | regressed 0 | unchanged 285]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv