[clangd] use printQualifiedName to skip the inlinenamespace qualifiers.

Summary:
symbols in libcpp are inside the inline namespace, printQualifierAsString will
print the inline namespace, which is unexpected.

Reviewers: kadircet

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75174