[llvm] [Github] Cancel previous in-progress code formatting jobs (PR #106701)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

CC @nicovank 

This doesn't replace the need to get rid of the checkout through merge base step in this workflow, but if this actually fixes the underlying timeout issue, that turns into an optimization rather than a correctness issue.

Once this lands, I'll monitor the run time of the PR code format job to see if there are any new timeouts to confirm if we've fixed it or not.

https://github.com/llvm/llvm-project/pull/106701