chore: add Kokoro back to required checks (#485)

* chore: add Kokoro back to required checks

* add samples checks too

Author: tswast

.github/sync-repo-settings.yaml

@@ -16,6 +16,12 @@ branchProtectionRules:
     - 'unit (3.9)'
     - 'unit (3.10)'
     - 'cover'
+    - 'Kokoro'
+    - 'Samples - Lint'
+    - 'Samples - Python 3.7'
+    - 'Samples - Python 3.8'
+    - 'Samples - Python 3.9'
+    - 'Samples - Python 3.10'
 permissionRules:
   - team: actools-python
     permission: admin