Only clear space if we're running the docker test, to save test time

.github/workflows/ci.yml

@@ -145,6 +145,7 @@ jobs:
       # We have seen issues with running out of disk space on test_docker
       - name: Free Disk Space (Ubuntu)
         uses: jlumbroso/free-disk-space@main
+        if: matrix.ci_pattern == 'tests/mock_vws/test_docker.py'
         with:
           # All of these default to true (meaning they are removed).
           docker-images: false