Revert D27408378: [quant][graphmode][fx][refactor] Factor out insert_observers_for_model to a separate function
Test Plan: revert-hammer
Differential Revision:
D27408378 (https://github.com/pytorch/pytorch/commit/c445f4ee939aad6d80bcdf5deb14e9259cf3994b)
Original commit changeset: 9143f0a6f939
fbshipit-source-id: ae65ea798a6d72f2ec724c4c1b492937edddf721
