[quant][docs] quantized model save/load instructions (#69789)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69789
Add details on how to save and load quantized models without hitting errors
Test Plan:
CI autogenerated docs
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D33030991
fbshipit-source-id: 8ec4610ae6d5bcbdd3c5e3bb725f2b06af960d52
