chore: purge old account support

[remyleone]

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Relates OR Closes #0000

Release note for CHANGELOG:

[codecov-commenter]

Codecov Report

Merging #3290 (c3a785f) into master (0dacbb8) will decrease coverage by 3.82%.
The diff coverage is 72.05%.

@@            Coverage Diff             @@
##           master    #3290      +/-   ##
==========================================
- Coverage   75.65%   71.83%   -3.82%     
==========================================
  Files         174      174              
  Lines       38386    38375      -11     
==========================================
- Hits        29041    27568    -1473     
- Misses       8290     9797    +1507     
+ Partials     1055     1010      -45     

Impacted Files	Coverage Δ
internal/namespaces/account/v3/error.go	0.00% <ø> (ø)
internal/namespaces/account/v3/custom.go	72.46% <72.05%> (ø)

... and 3 files with indirect coverage changes