fix: handle annotated git tags correctly in repo server cache

[aali309]

When using annotated git tags with auto-sync enabled but self-heal disabled, manual changes were getting reverted. This was happening because the repo server cache wasn't handling annotated tags correctly.

Fixes: #21548

See #20082 for detailed description of what caused the regression, but TL;DR: this behaviour is currently present in v2.11.x, v2.12.x, v2.13.x and current master

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
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• [x ] I have added a brief description of why this PR is necessary and/or what this PR solves.
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[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 11 lines in your changes missing coverage. Please review.

Project coverage is 55.70%. Comparing base (0973409) to head (3e5b8c9).

Files with missing lines	Patch %	Lines
reposerver/cache/cache.go	50.00%	10 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21771      +/-   ##
==========================================
+ Coverage   55.67%   55.70%   +0.02%     
==========================================
  Files         339      339              
  Lines       56838    56857      +19     
==========================================
+ Hits        31645    31672      +27     
+ Misses      22547    22541       -6     
+ Partials     2646     2644       -2     

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