[clang-tidy] Fix module registry name and description for Darwin clang-tidy module.

Summary: When creating the module, must have copy-pasted from the misc module, and forgotten to update the name/description of the module in the registry.

Reviewers: stephanemoore, benhamilton, gribozavr

Reviewed By: gribozavr

Subscribers: xazax.hun, cfe-commits

Tags: #clang, #clang-tools-extra, #llvm

Differential Revision: https://reviews.llvm.org/D68251

llvm-svn: 373304