[clang-tools-extra] [clang-tidy] Fix broken HeaderFilterRegex when read from config file (PR #133582)

[Yat Ho via cfe-commits]

tearfur wrote:

P.S. Just a heads up that `Fixes #118009, #121969, #133453` is not linking this PR to all 3 issues.

They need to be split to 3 `Fixes #xxx` lines.

https://github.com/llvm/llvm-project/pull/133582