[llvm] Changed Regex to accept /branch: and /cherry-pick: commands (PR #81002)

[Shourya Goel via llvm-commits]

Sh0g0-1758 wrote:

I think we can do that in this PR itself. Removing the branch command and adding regex support for the chery-pick command ? 

https://github.com/llvm/llvm-project/pull/81002