[clang] [clang][Diagnostics] Make 'note' color CYAN (PR #66997)

[Christopher Di Bella via cfe-commits]

cjdb wrote:

This doesn't really fix the problem, it just shuffles it around. I expect people with blue(ish) terminals will experience the same issue after this is applied, so we ought to try and detect what colours to print out, and then have compatible themes.

https://github.com/llvm/llvm-project/pull/66997