Errant GTID detection fix for VTOrc

[GuptaManan100]

Description

This PR fixes the issue described in #17286. The problem was fixed by adding a conditional check to see if the tablet we're detecting errant GTIDs on is the primary tablet itself.

Related Issue(s)

• Fixes Bug Report: VTOrc is detecting errant GTIDs on the primary #17286

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 67.40%. Comparing base (8648264) to head (36eda82).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vtorc/inst/instance_dao.go	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17287      +/-   ##
==========================================
- Coverage   67.40%   67.40%   -0.01%     
==========================================
  Files        1574     1574              
  Lines      253205   253209       +4     
==========================================
- Hits       170676   170664      -12     
- Misses      82529    82545      +16     

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[dbussink]

Looks like a good fix.