ConvPackedParams: remove legacy format (#43651)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43651
This is a forward compatibility follow-up to
https://github.com/pytorch/pytorch/pull/43086/. We switch the
conv serialization to output the v2 format instead of the v1 format.
The plan is to land this 1 - 2 weeks after the base PR.
Test Plan:
```
python test/test_quantization.py TestSerialization.test_conv2d_graph_v2
python test/test_quantization.py TestSerialization.test_conv2d_nobias_graph_v2
```
Imported from OSS
Reviewed By: z-a-f
Differential Revision: D23355480
fbshipit-source-id: 4cb04ed8b90a0e3e452297a411d641a15f6e625f
