[clangd] Fix DocumentSymbol ranges

Summary:
DocumentSymbol ranges were not previously tested and, as a result, had invalid
end location. This patch addresses the issue.

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D83668