[CI] Use --new-branch rebaseline-tests.yml

Author: sbc100

.github/workflows/rebaseline-tests.yml

@@ -40,7 +40,7 @@ jobs:
           git config user.name emscripten-bot
           git config user.email [email protected]
           ./bootstrap
-          if ./tools/maint/rebaseline_tests.py; then
+          if ./tools/maint/rebaseline_tests.py --new-branch; then
              echo "rebaseline_tests returned zero, expectations up-to-date"
              # Exit early and don't create a PR
              exit 0