[clang-format] Correctly annotate UDLs as OverloadedOperator

While the opening parenthesis of an user-defined literal operator was
correctly annotated as OverloadedOperatorLParen, the "" and its suffix
wasn't annotated as OverloadedOperator.

Fixes https://github.com/llvm/llvm-project/issues/58035

Differential Revision: https://reviews.llvm.org/D134853