[clang-format] fix nested angle brackets parse inside concept definition

Due to how parseBracedList always stopped on the first closing angle
bracket and was used in parsing angle bracketed expression inside concept
definition, nested brackets inside concepts were parsed incorrectly.

nextToken() call before calling parseBracedList is required because
we were processing opening angle bracket inside parseBracedList second
time leading to incorrect logic after my fix.

Fixes https://github.com/llvm/llvm-project/issues/54943
Fixes https://github.com/llvm/llvm-project/issues/54837

Reviewed By: HazardyKnusperkeks, curdeius

Differential Revision: https://reviews.llvm.org/D123896