[clangd] exclude check-clangd from check-all, fix buildbot failure.

check-clangd is included via check-clang-tools, otherwise we will run two
instances of check-clangd in parallel when running 'check-all',
which may have race condition.

llvm-svn: 343526
GitOrigin-RevId: 3e0c1bdbe41c980950cb0041d34cafbd967c2e3d
1 file changed