add import for test_quantizer.py (#25222)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25222
forgot to add import..
Test Plan:
python test/test_quantizer.py
Imported from OSS
Differential Revision: D17066193
fbshipit-source-id: 638119053724b21151eb6f05adfd39d094e44de7
