Only run scheduled python bindings generation on main repo

Author: knmcguire

.github/workflows/generate-bindings.yml

@@ -38,6 +38,10 @@ jobs:
             ros_distribution: rolling
             ros_version: 2
     runs-on: ubuntu-latest
+    if: |
+        github.event_name == 'workflow_dispatch' || (
+          github.event_name == 'schedule' && github.repository == 'ros2-rust/ros2_rust'
+        )
     permissions:
       contents: write
       pull-requests: write