[clang] fix(clang/**.py): fix invalid escape sequences (PR #94029)

[Balazs Benics via cfe-commits]

steakhal wrote:

Hi, could you explain the motivation of this patch?
I'm not an expert on Python, but to me it seemed like the `r"..."` strings are supposed to be used for regular expressions, and in this change you appear to transform those strings into plain old strings.
Could you help me understand this?

https://github.com/llvm/llvm-project/pull/94029