Use pyvista/setup-headless-display-action v4

Author: PProfizi

.github/workflows/docs.yml

@@ -110,7 +110,7 @@ jobs:
           python -c "from ansys.dpf import core"
 
       - name: "Setup headless display"
-        uses: pyvista/setup-headless-display-action@v2
+        uses: pyvista/setup-headless-display-action@48066dd0b79cf46babc16223a1dce3aa4803ec43 # v4.0
 
       - name: "Setup Graphviz"
         uses: ts-graphviz/setup-graphviz@v2