Revert D26626092: [quant][graphmode][fx][fp16] Add fp16 support for {add|mul}{_relu}
Test Plan: revert-hammer
Differential Revision:
D26626092 (https://github.com/pytorch/pytorch/commit/2962fbb03c68ae4fcabc58168f732cea900728b4)
Original commit changeset: 91d040efa51e
fbshipit-source-id: cc6bcc0f451d6adcd7bf7572451e6e3cd6ad59d1
