Fix flapping demo geo_location test (#37516)

tests/components/demo/test_geo_location.py

 """The tests for the demo platform."""
 import unittest
 
+import pytest
+
 from homeassistant.components import geo_location
 from homeassistant.components.demo.geo_location import (
     DEFAULT_UPDATE_INTERVAL,
@@ -20,6 +22,12 @@ from tests.common import (
 CONFIG = {geo_location.DOMAIN: [{"platform": "demo"}]}
 
 
+@pytest.fixture(autouse=True)
+def mock_legacy_time(legacy_patchable_time):
+    """Make time patchable for all the tests."""
+    yield
+
+
 class TestDemoPlatform(unittest.TestCase):
     """Test the demo platform."""