chore: bump go to v1.21.5

[jpadilla]

Description

Address the following vulnerabilities reported by govulncheck:

Vulnerability #1: GO-2023-2382
    Denial of service via chunk extensions in net/http

Vulnerability #2: GO-2023-2185
    Insecure parsing of Windows paths with a \??\ prefix in path/filepath

References

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ac3af79) 82.35% compared to head (b5fedbe) 82.36%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1219      +/-   ##
==========================================
+ Coverage   82.35%   82.36%   +0.02%     
==========================================
  Files          83       83              
  Lines        9587     9587              
==========================================
+ Hits         7894     7895       +1     
+ Misses       1340     1339       -1     
  Partials      353      353              

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