Add delay to test_modelChange()

Have seen this fail on macOS a couple of times, and once on Windows,
so the issue does not appear Windows-only, and the existing delay does
not appear to have been long enough in all cases.

pylib/tests/test_models.py

@@ -390,9 +390,7 @@ def test_modelChange():
     assert note.cards()[0].id == c1.id
     # delete first card
     map = {0: None, 1: 1}
-    if is_win:
-        # The low precision timer on Windows reveals a race condition
-        time.sleep(0.05)
+    time.sleep(0.25)
     col.models.change(basic, [note.id], basic, noop, map)
     note.load()
     c0.load()