This fixes a clangd rename issue, which is missing the reference of
an incomplete specialization.
Unfortunately, I didn't reproduce this issue in clang-rename, I guess
the input FoundDecl of AdditionalUSRFinder is different in clangd vs
clang-rename, clang-rename uses the underlying CXXRecordDecl of the
ClassTemplateDecl, which is fixed in https://github.com/llvm/llvm-project/commit/5d862c042b52ae2aad37471d0b83b6c678a520e3;
while clangd-rename uses the ClassTemplateDecl.
clang-format: please reformat the code