[clang-format] Fix invalid-code-generation by RemoveBracesLLVM

When removing an r_brace that is the first token of an annotated line, if the
line above ends with a line comment, clang-format generates invalid code by
merging the tokens after the r_brace into the line comment.

Fixes #56488.

Differential Revision: https://reviews.llvm.org/D129742