Clean up old bot infrastructure in repos

[BartMassey]

We have a bunch of repos that have triagebot and other configuration from olden times, which should probably be removed as unused to avoid confusion and complication. Here's James's triagebot search: https://github.com/search?type=code&q=org%3Arust-embedded+triagebot.toml

Help wanted.

[Kobzol]

I can clean that up, remove the triagebot access from those repos and send PRs to remove those configuration files.