Use static branch name

Author: agners

.github/workflows/dependency-update.yaml

@@ -53,5 +53,5 @@ jobs:
 
             See full diff at
             https://github.com/project-chip/connectedhomeip/compare/${{ steps.update-submodule.outputs.short_hash_before }}...${{ steps.update-submodule.outputs.short_hash }}.
-          branch: update-connectedhomeip-submodule-to-${{ steps.update-submodule.outputs.short_hash }}
+          branch: update-connectedhomeip-submodule-to-latest-master