bump mockito to version 5.4.1 (#4085)

Part of flutter/flutter#127226

Follow up to flutter/packages#3544. Version 5.4.0 from that PR is not new enough, see

```
Because mockito >=5.4.0 <5.4.1 depends on test_api >=0.2.1 <0.6.0 and every version of flutter_test from sdk depends on test_api 0.6.0, mockito >=5.4.0 <5.4.1 is incompatible with flutter_test from sdk.
So, because quick_actions_platform_interface depends on both flutter_test from sdk and mockito 5.4.0, version solving failed.
```

https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8780090492483790881/+/u/run_test.dart_for_flutter_plugins_shard_and_subshard_analyze/test_stdout

Author: christopherfujino

pubspec.yaml

@@ -28,5 +28,5 @@ dev_dependencies:
     sdk: flutter
   flutter_test:
     sdk: flutter
-  mockito: 5.4.0
+  mockito: 5.4.1
   pigeon: ^9.2.4