Add a timeout of 30 min

For all CI jobs. Based on some eye-balling 30 minutes should be
enough time for all jobs to complete.

pr-checks/sync.py

@@ -85,6 +85,7 @@ for file in os.listdir('checks'):
             }
         },
         'name': checkSpecification['name'],
+        'timeout-minutes': 30,
         'runs-on': '${{ matrix.os }}',
         'steps': steps
     }