Update FEATURE_GATES.md

[justindavies]

Move CombinedServicesFromDifferentHTTPRoutes to GA status. Keeping it still off by default initially.

What this PR does / why we need it:

Moving CombinedServicesFromDifferentHTTPRoutes to GA

Which issue this PR fixes:

N/A

Special notes for your reviewer:

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• [ ] the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[CLAassistant]

All committers have signed the CLA.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 58.4%. Comparing base (ea677ae) to head (6fbbceb). Report is 38 commits behind head on main.

:exclamation: There is a different number of reports uploaded between BASE (ea677ae) and HEAD (6fbbceb). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (ea677ae)	HEAD (6fbbceb)
	2	1

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #7511      +/-   ##
========================================
- Coverage   77.2%   58.4%   -18.9%     
========================================
  Files        220     221       +1     
  Lines      25414   25520     +106     
========================================
- Hits       19644   14925    -4719     
- Misses      4775    9906    +5131     
+ Partials     995     689     -306     

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[tao12345666333]

https://github.com/Kong/kubernetes-ingress-controller/pull/7569 has been merged, so we can close this one. Thanks