Revert D23916669: quant docs: add reduce_range explanatation to top level doc
Test Plan: revert-hammer
Differential Revision:
D23916669 (https://github.com/pytorch/pytorch/commit/eb3962439404cff611d83e932dafc77f3cf32d5f)
Original commit changeset: ef93fb774cb1
fbshipit-source-id: 7b56020427e76e13f847494044179c81d508db11
