The 5.1.0 release introduced two changes:

- Terraform plan jobs would trigger on all branch push events, including
feature branches.
- Manual Terraform apply jobs for development would be available in both
branch push event pipelines and merge request event pipelines.

This commit reverts the branch push event changes, as they require further
discussion. However, we will retain the manual development apply jobs in
merge request pipelines, as this appears to be a beneficial improvement.

fix: partially revert 5.1.0

See merge request !128