Fix wrong branch name in publish-to-testpypi config file

Author: ogrisel

.github/workflows/publish_to_pypi.yml

@@ -103,7 +103,7 @@ jobs:
     name: Publish cloudpickle 🥒 distribution 📦 to TestPyPI
     needs:
     - build
-    if: github.ref_name == 'main'
+    if: github.ref_name == 'master'
     runs-on: ubuntu-latest
 
     environment: