[clangd-vscode] Do not customize uri converters in vscode

Summary:
Clangd is already resolving symlinks on the server side, therefore
there is no more need to handle it in client side. This was also resulting in
breakages whenever index contained a symbol coming from a non-existent file(like
a generated file), e.g. during workspace symbols whole response was dropped
since stat had failed.

Reviewers: ilya-biryukov

Subscribers: MaskRay, jkorous, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D62288

llvm-svn: 361475