[ci] remove TD + test specification code from run_test.py
In the case of target determination, this is just removing comments that
refer to non-existent code.
In the case of the test specification code; this removes (what I believe
to be) an unused feature. If we're using this somehow let me know and I
can revise the PR.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79372
Approved by: https://github.com/janeyx99
