Fix test-projects.yml

Author: ondrejmirtes

.github/workflows/test-projects.yml

@@ -26,4 +26,4 @@ jobs:
           token: ${{ secrets.REPO_ACCESS_TOKEN }}
           repository: "${{ matrix.repository }}"
           event-type: test_phpstan
-          client-payload: '{"ref": "${{ github.ref_name }}"}'
+          client-payload: '{"ref": "2.1.x"}'