[clang] [KeyInstr][Clang][NFC] Don't set -dwarf-use-key-instructions (PR #144115)

[Jeremy Morse via cfe-commits]

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

LGTM (my least favourite part of github, aside from it not being Phabricator, is that it chucks away all the inline comments randomly. Yay).

Keeping on the HELP checklines though: if you symlink clang to `/bin/true` then with no checklines looking for a positive match, the test will still pass, which sucks. (This isn't related to this patches change in behaviour, so the patch can still land).

https://github.com/llvm/llvm-project/pull/144115