Do now allow prebuild re-triggering on successful prebuilds

[gtsiolis]

Problem to solve

Following up on the relevant discussion (internal) about triggering prebuilds, we should not allow users to trigger prebuilds for successful prebuilds. Cc @AlexTugarev @jankeromnes @svenefftinge

Good point! Let’s not allow retriggering when READY.

Leaving the trigger option could create more confusion, especially as 🅰️ the action verb changes remains the same regardless if the prebuild has succeded or failed and 🅱️ the verb changes on Branches and Prebuilds page (see #5008).

[AlexTugarev]

This is already done. I'm too lazy to search for the PR from @jankeromnes.

[gtsiolis]

Thanks @AlexTugarev! FWIW, This was resolved as part of #5836.