[docs] remove stale plugin recommendation (flutter#8450)

This plugin is no longer being maintained.

https://plugins.jetbrains.com/plugin/7345-presentation-assistant-for-2023-2/versions

<img width="875" height="222" alt="image" src="https://github.com/user-attachments/assets/3721f607-aa64-4e8d-a41c-1d436a0e86fb" />

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<details>
  <summary>Contribution guidelines:</summary><br>

- See our [contributor guide]([https://github.com/dart-lang/sdk/blob/main/CONTRIBUTING.md](https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview) for general expectations for PRs.
- Larger or significant changes should be discussed in an issue before creating a PR.
- Dart contributions to our repos should follow the [Dart style guide](https://dart.dev/guides/language/effective-dart) and use `dart format`.
- Java and Kotlin contributions should strive to follow Java and Kotlin best practices ([discussion](flutter#8098)).
</details>

Author: pq