Update documentation to note that null bytes are disallowed in method channel names.

## Steps to Reproduce

Linked to https://github.com/firebase/flutterfire/issues/9587

In FlutterFire, we are using channels with arbitrary names to listen to events emitted by native.
It appears that using a channel that has a Unicode character; the channel will fail with
```
MissingPluginException (MissingPluginException(No implementation found for method getPlatformVersion on channel hello))
```
**Expected results:**
We should be able to use Unicode characters in MethodChannels.

**Actual results:**

```
MissingPluginException (MissingPluginException(No implementation found for method getPlatformVersion on channel hello))
```

<details>
<summary>Code sample</summary>

By using `flutter create --org com.example --template=plugin --platforms=android,ios,linux,macos,windows -a kotlin hello``

And changing `hello_method_channel.dart:10`
```
final methodChannel = const MethodChannel('hello\u{0000}');
```

And `android/src/main/kotlin/com/example/hello/HelloPlugin.kt:20` with

```
channel = MethodChannel(flutterPluginBinding.binaryMessenger, "hello\u0000")
```

You will get the issue.

</details>

<details>
  <summary>Logs</summary>



```
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.3.9, on macOS 13.0 22A380 darwin-arm, locale en-FR)
[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 14.0.1)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2021.3)
[✓] VS Code (version 1.73.1)
[✓] Connected device (3 available)
[✓] HTTP Host Availability

• No issues found!
```

</details>

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Update documentation to note that null bytes are disallowed in method channel names. #116652

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Update documentation to note that null bytes are disallowed in method channel names. #116652

Description

Steps to Reproduce

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Metadata

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Labels

Type

Projects

Milestone

Relationships

Development

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