[clang] [clang] Fix the local parameter of void type inside the `Requires` expression. (PR #109831)

[via cfe-commits]

c8ef wrote:

```
      // C++23 [dcl.fct]p6:
      //   An explicit-object-parameter-declaration is a parameter-declaration
      //   with a this specifier. An explicit-object-parameter-declaration
      //   shall appear only as the first parameter-declaration of a
      //   parameter-declaration-list of either:
      //   - a member-declarator that declares a member function, or
      //   - a lambda-declarator.
      //
      // The parameter-declaration-list of a requires-expression is not such
      // a context.
```

See also: https://github.com/llvm/llvm-project/pull/88974

https://github.com/llvm/llvm-project/pull/109831