[clang] [clang][ci] Remove unnecessary BuildKite jobs for Clang (PR #93233)

[Tom Stellard via cfe-commits]

https://github.com/tstellar commented:

If we aren't running the tests any more, can we build clang with `-DLLVM_TARGETS_TO_BUILD=Native`

https://github.com/llvm/llvm-project/pull/93233