Fix mocks not compatible with Dart 2.15 causing test failures (cfug#1847

)

* revert mockito version and mocks

This PR just reverts some recent changes to mocks which are not
supported on Dart 2.15 and cause some CI tests to fail.
The test failures have gone unnoticed due to all the noise around
httpbin not working.

When merging this change to the 6.0.0 branch, we need to make sure to
skip this.

### New Pull Request Checklist

- [x] I have read the
[Documentation](https://pub.dev/documentation/dio/latest/)
- [x] I have searched for a similar pull request in the
[project](https://github.com/cfug/dio/pulls) and found none
- [x] I have updated this branch with the latest `main` branch to avoid
conflicts (via merge from master or rebase)
- [ ] I have added the required tests to prove the fix/feature I'm
adding
- [ ] I have updated the documentation (if necessary)
- [x] I have run the tests without failures
- [ ] I have updated the `CHANGELOG.md` in the corresponding package

dio/pubspec.yaml

@@ -25,5 +25,5 @@ dev_dependencies:
   test: ^1.5.1
   coverage: ^1.0.3
   crypto: ^3.0.2
-  mockito: ^5.3.0
+  mockito: ^5.2.0
   build_runner: any

dio/test/cancel_token_test.dart

@@ -62,7 +62,7 @@ void main() {
         );
       }
 
-      await Future.delayed(const Duration(milliseconds: 5));
+      await Future.delayed(const Duration(milliseconds: 50));
       token.cancel(reason);
 
       expect(requests, hasLength(2));

dio/test/mock/http_mock.dart

@@ -6,12 +6,15 @@ import 'http_mock.mocks.dart';
 
 final httpClientMock = MockHttpClient();
 
-@GenerateNiceMocks([
-  MockSpec<HttpClient>(),
-  MockSpec<HttpClientRequest>(),
-  MockSpec<HttpClientResponse>(),
-  MockSpec<HttpHeaders>(),
-])
+@GenerateMocks(
+  [],
+  customMocks: [
+    MockSpec<HttpClient>(),
+    MockSpec<HttpClientRequest>(),
+    MockSpec<HttpClientResponse>(),
+    MockSpec<HttpHeaders>(),
+  ],
+)
 class MockHttpOverrides extends HttpOverrides {
   @override
   HttpClient createHttpClient(SecurityContext? context) {