Fixes [TabBar labelStyle.color and unselectedLabelStyle.color does not take effect](https://github.com/flutter/flutter/issues/109484)

### Code sample

<details>
<summary>expand to view the code sample</summary> 

```dart
import 'package:flutter/material.dart';

/// Flutter code sample for [TabBar].

const Color labelColor = Color(0xFFFF0000);
const Color unselectedLabelColor = Color(0x95FF0000);
const TextStyle labelStyle = TextStyle(
  color: Color(0xff0000ff),
  fontWeight: FontWeight.bold,
);
const TextStyle unselectedLabelStyle = TextStyle(
  color: Color(0x950000ff),
  fontStyle: FontStyle.italic,
);

void main() => runApp(const TabBarApp());

class TabBarApp extends StatelessWidget {
  const TabBarApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(useMaterial3: true),
      home: const TabBarExample(),
    );
  }
}

class TabBarExample extends StatelessWidget {
  const TabBarExample({super.key});

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      initialIndex: 1,
      length: 3,
      child: Scaffold(
        appBar: AppBar(
          title: const Text('TabBar Sample'),
          bottom: const TabBar(
            // labelColor: labelColor,
            // unselectedLabelColor: unselectedLabelColor,
            labelStyle: labelStyle,
            unselectedLabelStyle: unselectedLabelStyle,
            tabs: <Widget>[
              Tab(
                icon: Icon(Icons.cloud_outlined),
                text: 'Cloudy',
              ),
              Tab(
                icon: Icon(Icons.beach_access_sharp),
                text: 'Sunny',
              ),
              Tab(
                icon: Icon(Icons.brightness_5_sharp),
                text: 'Rainy',
              ),
            ],
          ),
        ),
        body: const TabBarView(
          children: <Widget>[
            Center(
              child: Text("It's cloudy here"),
            ),
            Center(
              child: Text("It's rainy here"),
            ),
            Center(
              child: Text("It's sunny here"),
            ),
          ],
        ),
      ),
    );
  }
}
```

</details>

#### When `labelStyle` and `unselectedLabelStyle` are specified with a color.

### Before
![image](https://github.com/flutter/flutter/assets/48603081/4138f928-aa63-40bc-9d4e-4d2aeefe72c1)

### After

![image](https://github.com/flutter/flutter/assets/48603081/2ce552c5-3972-4b5d-9492-eb487764e58f)