Test Clock: Fix timezone offset

This was previously removed, and now this test seems to depend on the
environment it is being ran (?). This adds back the UTC offset of the
timezone such that the delta is taken into account. Fixes qtile#4762

test/widgets/test_clock.py

@@ -43,6 +43,11 @@ class MockDatetime(datetime.datetime):
     def now(cls, *args, **kwargs):
         return cls(2021, 1, 1, 10, 20, 30)
 
+    def astimezone(self, tzone=None):
+        if tzone is None:
+            return self
+        return self + tzone.utcoffset(None)
+
 
 @pytest.fixture
 def patched_clock(monkeypatch):