scratch-built-bot: always create only a single commit rendering the templates

[dcermak]

Currently the bot creates a new PR from the branch for-deploy-$SP by rendering the templates. If changes are made after the PR is created, then the bot creates an additional commit. However, this can cause problems if a revert is pushed to main as then there's a second commit reverting the first in the PR confusing the remaining github actions. If the bot always created only a single entry, then this could be avoided.