[clang] [clang-tools-extra] [flang] [lld] [llvm] [LLVM][utils] Add script which clears release notes (PR #153593)

[Yanzuo Liu via cfe-commits]

zwuis wrote:

Thank you for your review!

> @zwuis do you need someone to merge the PR for you?

I can merge the PR by myself :)

https://github.com/llvm/llvm-project/pull/153593