Fix workflow file

Author: cbespin

.github/workflows/tests.yml

@@ -24,7 +24,7 @@ jobs:
         plugin_online_monitor pymosa/online_monitor
 
     - name: Headless display setup
-    - uses: pyvista/setup-headless-display-action@v3
+      uses: pyvista/setup-headless-display-action@v3
       with:
         qt: true