Remove the optional dependency from libclang to clang-tidy/include-fixer

clangd does a better job on both of these, so don't slow down everyone's build
for a poorly working libclang feature.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@347496 91177308-0d34-0410-b5e6-96231b3b80d8