[clang-tools-extra] [clang-tidy] Add a release note about unchecked-optional-access smart pointer caching (PR #122290)

[Congcong Cai via cfe-commits]

https://github.com/HerrCai0907 approved this pull request.

does check doc need to be changed also?

https://github.com/llvm/llvm-project/pull/122290