[clangd] Fix a regression issue in local rename.

Summary:
The regression is that we can't rename symbols in annonymous
namespaces.

Reviewers: ilya-biryukov

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70853