Update service labels in NFR tests

[sjberman]

Problem: The GKE service label for nginx LB is not provided in the helm chart anymore.

Solution: Add the label in each Gateway infrastructure field.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.79%. Comparing base (06fa2e6) to head (a9a46d4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3386      +/-   ##
==========================================
+ Coverage   86.76%   86.79%   +0.03%     
==========================================
  Files         129      129              
  Lines       14862    14862              
  Branches       62       62              
==========================================
+ Hits        12895    12900       +5     
+ Misses       1819     1815       -4     
+ Partials      148      147       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.