[BE] Delete `pre-cxx-11-abi MacOS libtorch builds (#96301)
Those ABI flags makes sense only for Linux, libc++ binaries shipped with MacOS has only one ABI flavor.
Moreover, those binaries were uploaded to the same location anyway, see
[upload job for pre-cxx-11 abi](https://github.com/pytorch/pytorch/actions/runs/4362299843/jobs/7628815268#step:7:97) and [upload job for cxx-11 abi](https://github.com/pytorch/pytorch/actions/runs/4362299812/jobs/7628879450#step:7:97)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96301
Approved by: https://github.com/atalman
