Build/Test Tools: Change file filters for testing old branches.

This adds the `reusable-phpunit-tests-v3.yml` file to the list of changes that will run the `test-old-branches.yml` workflow.

There are several numbered branches that reference this reusable workflow, so any changes should be verified across all calling branches.

See #64893.

git-svn-id: https://develop.svn.wordpress.org/trunk@62535 602fd350-edb4-49c9-b593-d223f7449a82

Author: desrosj

.github/workflows/test-old-branches.yml

@@ -7,7 +7,7 @@ on:
       - trunk
     paths:
       - '.github/workflows/test-old-branches.yml'
-      - '.github/workflows/reusable-phpunit-tests-v[1-2].yml'
+      - '.github/workflows/reusable-phpunit-tests-v[1-3].yml'
   # Run twice a month on the 1st and 15th at 00:00 UTC.
   schedule:
     - cron: '0 0 1 * *'