[clang-format] Correctly annotate star/amp in function pointer params

[clang-format] Correctly annotate star/amp in function pointer params

Inside the arguments part of a function pointer declaration,
`determineStarAmpUsage` results in a binary operator rather than
pointers, because said parens are assumed to be an expression.

This patch correctly marks the argument parens of a function
pointer type as not an expression. Note that this fix already
existed for Objective-C blocks as part of f1f267b447f60528440d2c066b29ab014ae7f90f.
As Objective-C blocks and C/C++ function pointers share a lot
of the same logic, that fix also makes sense here.

Fixes https://github.com/llvm/llvm-project/issues/31659

Differential Revision: https://reviews.llvm.org/D135707