Build/Test Tools: Pin Gutenberg version for 6.5 branch.

The minimum required version of WordPress for the Gutenberg plugin as of version 19.8.0 is now 6.6. This pins the final version that supported WordPress 6.5 to ensure E2E tests continue to pass.

Props bernhard-reiter.
Fixes 62488.

git-svn-id: https://develop.svn.wordpress.org/branches/6.5@59518 602fd350-edb4-49c9-b593-d223f7449a82

Author: desrosj

.github/workflows/end-to-end-tests.yml

@@ -48,6 +48,7 @@ jobs:
         LOCAL_SCRIPT_DEBUG: [ true, false ]
     with:
       LOCAL_SCRIPT_DEBUG: ${{ matrix.LOCAL_SCRIPT_DEBUG }}
+      gutenberg-version: '19.7.0'
 
   slack-notifications:
     name: Slack Notifications