fix(ci): pin Kong/kong-license to a commit SHA instead of @master

[cv1002]

Summary

• Kong/kong-license's master branch has no branch protection, so the unpinned Kong/kong-license@master reference in integration-ai-gateway.yaml lets anyone with push access to that repo run code in this repo's CI, which has access to secrets.
• Pins the action to the current master tip (ddccb487a0b319cef85f348b16a1ad2b6d9c1df7), the same SHA already used by other Kong repos (e.g. kong-ee) and by this repo's own other workflows.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 35.92%. Comparing base (39f1ee2) to head (83d0d26).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2178   +/-   ##
=======================================
  Coverage   35.92%   35.92%           
=======================================
  Files          82       82           
  Lines        7832     7832           
=======================================
  Hits         2814     2814           
  Misses       4753     4753           
  Partials      265      265           

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