Try to workaround empty GITHUB_REF bug of GitHub runners

Author: michaelosthege

.github/workflows/release.yml

@@ -36,6 +36,7 @@ jobs:
         python setup.py sdist bdist_wheel
     - name: Check version number match
       run: |
+        export GITHUB_REF=refs/tags/${{ github.event.release.tag_name }}
         echo "GITHUB_REF: ${GITHUB_REF}"
         # Make sure the package version is the same as the tag
         grep -Rq "^Version: ${GITHUB_REF:11}$" mcbackend.egg-info/PKG-INFO