[clang-format] Concepts: allow identifiers after negation

Previously, the formatter would refuse to treat identifiers within a
compound concept definition as actually part of the definition, if
they were after the negation operator !. It is now made consistent
with the likes of && and ||.

Fixes https://github.com/llvm/llvm-project/issues/55898

Differential Revision: https://reviews.llvm.org/D131978