[clang] [Sema] Fixed faulty shift count warning (PR #69521)

[Erich Keane via cfe-commits]

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

Alright, looks like @shafik isn't going to review this, so I'll just have to accept it.  LGTM.

https://github.com/llvm/llvm-project/pull/69521