[clang] [Clang][Sema] fix noexecpt mismatch of friend declaration (PR #102267)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

I don't think this is the right approach. What I think we _should_ be doing is to compare the operands of the _noexcept-specifier_ the same way we compare constraints (i.e. substitute so all references to template parameters have the correct depth and _then_ check whether the substituted expressions are equivalent). WDYT @mizvekov? 

https://github.com/llvm/llvm-project/pull/102267