MAINT fix placeholder with correct package name in test.pypi.org publ…

…ishing config (#550)

.github/workflows/publish_to_pypi.yml

@@ -104,7 +104,7 @@ jobs:
 
     environment:
       name: testpypi
-      url: https://test.pypi.org/p/<package-name>
+      url: https://test.pypi.org/p/cloudpickle
 
     permissions:
       id-token: write  # IMPORTANT: mandatory for trusted publishing