[clang] [clang][Parse] Use consistent Scope::ScopeFlags enum values (NFC) (PR #159275)

[Bruno De Fraine via cfe-commits]

brunodf-snps wrote:

Tagging @cor3ntin @erichkeane @Sirraide 
(Feel free to merge this if you approve, I have no commit access.)

https://github.com/llvm/llvm-project/pull/159275