[clangd] Disable all dependency outputs

Summary: Fixes https://github.com/clangd/clangd/issues/322

Reviewers: sammccall

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78833

(cherry picked from commit 294b9d43)

Fixes https://github.com/clangd/clangd/issues/422