refactor: remove unnecessary error checking in PostgresAdapter

[cbaker6]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

There are unnecessary error checks in PostgresStorageAdapter.js that were left over from adding IF NOT EXISTS in #6741 and #6506

Related issue: #6741 and #6506

Approach

Remove error checks and code that isn't used anymore.

TODOs before merging

• Add tests
• A changelog entry is created automatically using the pull request title (do not manually add a changelog entry)

[parse-github-assistant]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[codecov]

Codecov Report

Merging #7761 (9f80210) into alpha (7af5de4) will increase coverage by 0.02%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##            alpha    #7761      +/-   ##
==========================================
+ Coverage   93.96%   93.99%   +0.02%     
==========================================
  Files         183      183              
  Lines       13640    13635       -5     
==========================================
- Hits        12817    12816       -1     
+ Misses        823      819       -4     

Impacted Files	Coverage Δ
...dapters/Storage/Postgres/PostgresStorageAdapter.js	95.86% <50.00%> (+0.36%)	⬆️
src/ParseServerRESTController.js	97.01% <0.00%> (-1.50%)	⬇️
src/RestWrite.js	94.04% <0.00%> (ø)

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[cbaker6]

@mtrezza this is ready for review.

[mtrezza]

Looks good

[parseplatformorg]

🎉 This change has been released in version 5.0.0-alpha.16

[parseplatformorg]

🎉 This change has been released in version 5.0.0-beta.10

[parseplatformorg]

🎉 This change has been released in version 5.1.0