add type annotations to torch.nn.quantized.modules.conv (#49702)
Summary:
closes gh-49700
No mypy issues were found in the first three entries deleted from `mypy.ini`:
```
[mypy-torch.nn.qat.modules.activations]
ignore_errors = True
[mypy-torch.nn.qat.modules.conv]
ignore_errors = True
[mypy-torch.nn.quantized.dynamic.modules.linear]
ignore_errors = True
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49702
Reviewed By: walterddr, zou3519
Differential Revision: D25767119
Pulled By: ezyang
fbshipit-source-id: cb83e53549a299538e1b154cf8b79e3280f7392a
