[clang] Don't wrap immediate invocations in ConstantExprs within constexpr initializers (PR #89565)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

This seems reasonable to me, I think @cor3ntin should also approve before committing though.

https://github.com/llvm/llvm-project/pull/89565