[clang] [clang] SourceLocIdentKind::Function should not be dependent (PR #94942)

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cor3ntin wrote:

So, looked into this more.
You are correct that `Function` needs not be dependent because we only ever show the name of the function unqualified.
However, `FunctionSig` does.
Here is an example of what we are trying to preserve https://godbolt.org/z/M3eTa8nn5 (the clang 17 behavior was incorrect)

I apologize for not realizing earlier that your change was actually sensible in the case of `Function`

https://github.com/llvm/llvm-project/pull/94942