[lld-macho] Remove linking bitcode support

Apple deprecated bitcode in the deployment process in Xcode 14.0. Last
month Apple started requiring Xcode 14.1+ to submit apps to the App
Store. Since there isn't a use for bundling bitcode outside of
submitting to the App Store we should be safe to delete this handling
entirely from LLD.

Differential Revision: https://reviews.llvm.org/D150697