[bug] `json_serializable` is unable to handle enum with generics

Hello there.

Try this out:
```dart
import 'package:json_annotation/json_annotation.dart';

part 'asdlol_dto.g.dart';

enum Slug {
asd(),
lol(),
rofl(),
lmao<(int, int)>();

const Slug();
}

@JsonSerializable()
class Serializable {
const Serializable(this.slug);
final Slug slug;
}
```

JsonSerializable generates this code:
```dart
// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'asdlol_dto.dart';

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

Serializable _$SerializableFromJson(Map json) =>
$checkedCreate('Serializable', json, ($checkedConvert) {
final val = Serializable(
$checkedConvert('slug', (v) => $enumDecode(_$SlugEnumMap, v)),
);
return val;
});

Map _$SerializableToJson(Serializable instance) =>
{'slug': _$SlugEnumMap[instance.slug]!};

const _$SlugEnumMap = {
Slug.asd: 'asd',
Slug.lol: 'lol',
Slug.rofl: 'rofl',
Slug.lmao: 'lmao',
};
```

But the above errors at analysis time, since `_$SlugEnumMap` is incorrectly typed.
```
The argument type 'Map, String>' can't be assigned to the parameter type 'Map, String>'. [[argument_type_not_assignable](https://dart.dev/tools/diagnostics/argument_type_not_assignable?utm_source=dartdev&utm_medium=redir&utm_id=diagcode&utm_content=argument_type_not_assignable)]
```

I'm not sure what I can do on my end to fix of even to circumvent this.