Revert D28197820: [JIT][NNC] add hardswish symbolic gradient and NNC lowering
Test Plan: revert-hammer
Differential Revision:
D28197820 (https://github.com/pytorch/pytorch/commit/0142fd0b5798f1d21960ef022097ac401445d382)
Original commit changeset: 05305d85c5bb
fbshipit-source-id: 2e1d9699515982ba2a9be06e83a2ce043ec857ee
