[clang] Fix -Wunused-lambda-capture in TokenAnnotator.cpp (NFC)

llvm-project/clang/lib/Format/TokenAnnotator.cpp:2707:43:
error: lambda capture 'this' is not used [-Werror,-Wunused-lambda-capture]
    auto IsQualifiedPointerOrReference = [this](FormatToken *T) {
                                          ^~~~
1 error generated.