Update generated header to use flatbuffer v1.12; (#71279)
Summary:
Update generated header to use flatbuffer v1.12;
Also pin flatbuffer repo to v1.12
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71279
Test Plan:
unittest
Fixes #ISSUE_NUMBER
Reviewed By: gmagogsfm
Differential Revision: D33572140
Pulled By: qihqi
fbshipit-source-id: 319efc70f6c491c66a3dfcd7cad1f7defe69916b
