[quant][fix] Remove activation_post_process in qat modules (#42343)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42343
Currently activation_post_process are inserted by default in qat modules, which is not
friendly to automatic quantization tools, this PR removes them.
Test Plan: Imported from OSS
Reviewed By: raghuramank100
Differential Revision: D22856816
fbshipit-source-id: 988a43bce46a992b38fd0d469929f89e5b046131
