[clang] [clang][clang-scan-deps] Add LangOptions::AllowLiteralDigitSeparator to fix #88896 (PR #184235)

[Naveen Seth Hanig via cfe-commits]

naveen-seth wrote:

Only a one-line change from PR (#158420) to fix failing tests related to clang-format.
Set @tsfn as the primary author. Thanks for the original PR!

https://github.com/llvm/llvm-project/pull/184235