Add go-router v7 and v8 breaking change redirects

[chunhtai]

Description of what this PR is changing or adding, and why:

Issues fixed by this PR (if any):

Presubmit checklist

• This PR doesn’t contain automatically generated corrections (Grammarly or similar).
• This PR follows the Google Developer Documentation Style Guidelines — for example, it doesn’t use i.e. or e.g., and it avoids I and we (first person).
• This PR uses semantic line breaks of 80 characters or fewer.

[github-actions]

Visit the preview URL for this PR (updated for commit 8946763):

https://flutter-docs-prod--pr8853-chunhtai-patch-1-ronrzrzc.web.app

_{(expires Wed, 21 Jun 2023 22:00:21 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: d5ba327eec813901cac8396c4f458b02288624ab}

[parlough]

Thanks!