chore(#1109): remove the temporary branch trigger from the macOS lane

Run 42718673916 proved the lane end to end on this branch: Apple
accepted the submission, the staple validated, and spctl reported
"source=Notarized Developer ID". The lane now runs only when
release-signed.yml calls it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/macos-signed.yml

@@ -34,11 +34,6 @@ name: macOS signed build
 
 on:
   workflow_call:
-  # Proves the lane before a release tag (#1109). Removed before this branch
-  # merges.
-  push:
-    branches:
-      - feat/1109-macos-signing
 
 permissions:
   contents: read