Reference Issues/PRs

Fixes #26419

What does this implement/fix? Explain your changes.

• Removes non-functional twitter.yml workflow
• Removes references to the sklearn_commits twitter account that the workflow updated

Any other comments?

• Technically this is not a "fix", but there was no objection to removing
• I'm not sure if there are more technical things to update, whether in repo or out of it (especially secret values)
• I'm not sure if there are communications to update (i.e. explain somewhere why the account is now abandoned, or delete it but explain that it used to exist, simply ignore it, etc)