chore: Remove unnecessary assert in test

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: allenporter

tests/devices/test_device_manager.py

@@ -320,7 +320,6 @@ async def mock_home_data_with_counter(*args, **kwargs) -> HomeData:
 
         new_device = await device_manager.get_device("new_device_duid")
         assert new_device
-        assert new_device is not None
         assert new_device.name == "New Device"
 
         # Ensure closing again works without error