Delete the legacy `pages-build-deployment` github action

Link: https://github.com/flutter/devtools/actions/workflows/pages/pages-build-deployment

This is a legacy action that was for the old Jekyll-based documentation. These docs haven't been used in years, and the redirects were recently deleted from our repo, which is why the github action is now failing.

I cannot see a way to delete the action. Maybe I don't have permissions? @Piinks or @devoncarew do you know how we can delete this action from the flutter/devtools repo?

Start with the linked pages-build-deployment workflow in the flutter/devtools repository and check how the legacy GitHub Action is managed. Confirm whether repository permissions are required to remove it. Done means the obsolete action is deleted or disabled and its failing runs no longer occur.

Scritto dal modello di indicizzazione a partire dal testo della issue.