Due to the [recent cost-cutting](apache#14376), we are no longer running PR Merge Jobs in the `nuttx` and `nuttx-apps` repos. For this to happen, I am now running a script on my computer that will cancel any PR Merge Jobs that appear: [kill-push-master.sh](https://github.com/lupyuen/nuttx-release/blob/main/kill-push-master.sh)
This PR disables PR Merge Jobs permanently, so that we no longer need to run the script. This prevents our CI Charges from over-running, in case the script fails to operate properly.

Merged