Remove unnecessary patch from panel_custom tests (#146695)

tests/components/panel_custom/test_init.py

@@ -1,7 +1,5 @@
 """The tests for the panel_custom component."""
 
-from unittest.mock import Mock, patch
-
 from homeassistant import setup
 from homeassistant.components import frontend, panel_custom
 from homeassistant.core import HomeAssistant
@@ -22,7 +20,6 @@ async def test_webcomponent_custom_path_not_found(hass: HomeAssistant) -> None:
         }
     }
 
-    with patch("os.path.isfile", Mock(return_value=False)):
     result = await setup.async_setup_component(hass, "panel_custom", config)
     assert not result