CI: tentative enabling of tests workflow for merge group (#2933)

.github/workflows/tests.yaml

@@ -16,14 +16,9 @@ on:
       - '!CODEOWNERS'
       - '!.git*'
   pull_request_target:
-    paths:
-      # Conservatively run the tests. However, skip them if the only paths in
-      # the pull request match files that we know don't impact the build.
-      - '**'
-      - '!**/*.md'
-      - '!LICENSE'
-      - '!CODEOWNERS'
-      - '!.git*'
+    paths: ${{ push.paths }}
+  merge_group:
+    paths: ${{ push.paths }}
 
 # Cancel previous workflows on the PR when there are multiple fast commits.
 # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#concurrency