[quant] Factoring out the list of no_observers (#50459)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50459
Some of the custom modules cannot have the observers be inserted automatically. This PR factors out that list into a separate function.
Test is not required, as it is covered by the unittests for those modules.
(Note: this ignores all push blocking failures!)
Test Plan: Imported from OSS
Reviewed By: vkuzo
Differential Revision: D26092531
fbshipit-source-id: 1f89daf3a13ef31bc4e9058c3443559c65a05812
