Revert removed download for DioMixin (#1916)

See https://github.com/cfug/dio/pull/1772/files#r1281588318.

Fixes parse-community/Parse-SDK-Flutter#958.

### 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
- [x] I have updated the `CHANGELOG.md` in the corresponding package

---------

Signed-off-by: Alex Li <github@alexv525.com>

dio/CHANGELOG.md

@@ -5,7 +5,7 @@ See the [Migration Guide][] for the complete breaking changes list.**
 
 ## Unreleased
 
-*None.*
+- Revert removed `download` for `DioMixin`.
 
 ## 5.3.1
 

dio/lib/src/dio_mixin.dart

@@ -293,6 +293,21 @@ abstract class DioMixin implements Dio {
     );
   }
 
+  @override
+  Future<Response> download(
+    String urlPath,
+    dynamic savePath, {
+    ProgressCallback? onReceiveProgress,
+    Map<String, dynamic>? queryParameters,
+    CancelToken? cancelToken,
+    bool deleteOnError = true,
+    String lengthHeader = Headers.contentLengthHeader,
+    Object? data,
+    Options? options,
+  }) {
+    throw UnimplementedError();
+  }
+
   @override
   Future<Response<T>> requestUri<T>(
     Uri uri, {

dio/test/dio_mixin_test.dart

@@ -16,4 +16,13 @@ void main() {
     );
     expect(typedResponse.data, isNull);
   });
+
+  test('throws UnimplementedError when calling download', () {
+    expectLater(
+      () => _TestDioMixin().download('a', 'b'),
+      throwsA(TypeMatcher<UnimplementedError>()),
+    );
+  });
 }
+
+class _TestDioMixin with DioMixin implements Dio {}