[clang-tidy] adjust scripts to subsubsections in Release Notes

Summary:
I added subsubsections for typical Clang-tidy entries in Release Notes, so now scripts are aware of this changes.

I don't have GitHub commit access, so please commit changes.

Reviewers: aaron.ballman, alexfh, hokein

Reviewed By: alexfh

Subscribers: njames93, xazax.hun, cfe-commits

Tags: #clang-tools-extra, #clang

Differential Revision: https://reviews.llvm.org/D72527