Suggested macro expansion is slightly different from definition

As shown on screenshot below, there is an excessive whitespace between `clang` and `::`.
![image](https://github.com/llvm/llvm-project/assets/12883766/b8309e20-ead8-4e34-b43e-4b405e049778)

Observed while working on https://github.com/llvm/llvm-project/pull/70349
