[quant] Remove TensorListObserver (#38584)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38584
All observers will support tensor lists in future PR
Test Plan: Imported from OSS
Differential Revision: D21623464
fbshipit-source-id: c5c57ecfe14f7c3aa92b7c99d724e846132ae03b
