Upgrade the golang version used vitess-mixin

[frouioui]

Description

Until we find out what we want to do with vitess-mixin this PR upgrades the golang version to what we use in the rest of the codebase and update the golang upgrade tool to also upgrade the go.mod of vitess-mixin in the future.

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

• Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

Documentation

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• There should be some code comments as to why things are implemented the way they are.
• There should be a comment at the top of each new or modified test to explain what the test does.

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Backward compatibility

• Protobuf changes should be wire-compatible.
• Changes to _vt tables and RPCs need to be backward compatible.
• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 68.44%. Comparing base (9911880) to head (b006ffc).

Files	Patch %	Lines
go/tools/go-upgrade/go-upgrade.go	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15972      +/-   ##
==========================================
- Coverage   68.45%   68.44%   -0.01%     
==========================================
  Files        1562     1562              
  Lines      197057   197059       +2     
==========================================
- Hits       134891   134881      -10     
- Misses      62166    62178      +12     

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