[clang] [NFC][clang-scan-deps] Refine the implementation of dependency_directives_scan::Token::isOneOf (PR #150433)

[Erich Keane via cfe-commits]

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

This seems fine to me, though SEEING this dependency-scanner just brings up more questions than anything :) 

https://github.com/llvm/llvm-project/pull/150433