[CI] Improve `codenotify` workflow (#28432)

* Add path filtering to codenotify workflow

* Upgrade action to its latest version (v0.6.4)

.github/workflows/codenotify.yml

@@ -3,6 +3,11 @@ name: Codenotify
 on:
   pull_request:
     types: [opened, synchronize, ready_for_review]
+    # We're currently notifying developers only for frontend source changes.
+    # Update this glob if that ever changes and we start including backend source code changes.
+    paths:
+      - 'frontend/src/metabase/**'
+      - 'enterprise/frontend/src/metabase-enterprise/**'
 
 jobs:
   codenotify:
@@ -12,6 +17,6 @@ jobs:
       - uses: actions/checkout@v3
         with:
           ref: ${{ github.event.pull_request.head.sha }}
-      - uses: sourcegraph/codenotify@v0.4
+      - uses: sourcegraph/codenotify@v0.6.4
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}