Explicitly define github token env variable

.github/workflows/update-mod-versions.yml

@@ -25,6 +25,9 @@ jobs:
           python -m pip install --upgrade pip
           pip install requests
           
+      - env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Update mod versions
         run: |
           python .github/scripts/update_mod_versions.py