[clangd] No need to query ctor refs in cross-file rename.

Summary:
This patch reverts https://github.com/llvm/llvm-project/commit/2c5ee78de113484978450b834498e1b0e2aab5c4,
now kythe (https://github.com/kythe/kythe/issues/4381) supports returning ctors refs as part of class references, so
there is no need to query the ctor refs in the index (this would also
make the results worse, lots of duplications)

Reviewers: sammccall

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75439