Bring back Retry

[pbrisbin]

Presently, you can "retry" a Restyle by:

• git commit --amend --no-edit && git push --force
• git commit --allow-empty --message "Trigger CI" && git push

The former requires no extra commit but does require a force-push. The latter creates an unnecessary commit, though it will be (automatically) removed on rebase (even through GitHub).

We used to have an actual Retry feature, a button on the Job page. It was high complexity for little usage, but I've now had a user or two ask about it. We should consider bringing it back.