Reset Key Bindings to Default in Prefseditor Test

This commit adds a function that resets key bindings to the default in
 `test_keybinding_edit_produce_expected_accels` test.
Note that this function needs to run at the end of every test that
modifies the key bindings as they are not automatically reset after
the test has run.

tests/test_prefseditor_keybindings.py

@@ -252,6 +252,8 @@ def test_keybinding_edit_produce_expected_accels(
 
     assert accel_after_edit == expected_accel
 
+    reset_config_keybindings()
+
 
 @pytest.mark.parametrize(
     "accel_params",