Fix workflow file

Author: xcompass

.github/workflows/build.yml

@@ -24,7 +24,7 @@ jobs:
     - name: Check disk space
       run: df . -h
     - name: Free disk space
-        run: |
+      run: |
           sudo docker rmi $(docker image ls -aq) >/dev/null 2>&1 || true
           sudo rm -rf \
             /usr/share/dotnet /usr/local/lib/android /opt/ghc \