the lk agent delete doesn't have silent mode

[mhamri]

I am trying to delete the agent during cicd and recreate it again. but lk agent delete --id $ExistingAgent always is asking for confirmation and there isn't any --silent mode in it

[real-danm]

for cicd you can use this repo to make things simpler: https://github.com/livekit/deploy-action
I have not yet implemented delete there yet though, so added the silent flag for delete in #723