fix: Image cache path

Author: AlejandroFernandezLuces

.github/workflows/ci_cd.yml

@@ -125,7 +125,7 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           name: pytest-pyvista-images-${{ runner.os }}
-          path: tests/graphics/image_cache
+          path: tests/_image_cache
           retention-days: 7
 
       - uses: codecov/codecov-action@v5