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

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cor3ntin 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.

Not really, CYAN is only cyan if that's what your terminal decides to render the color 6 as, you can configure it to be orange if you want.

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