Some minor fix to unblock the Bert model quantization (#20787)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20787
Set requires_grad=False for bias: this will block the jit tracing.
The as_type fix: The input tensor shape and output tensor shape will be different, which will trigger the assertion failure at https://fburl.com/0m8xy7tc.
Reviewed By: jamesr66a
Differential Revision: D15445092
fbshipit-source-id: 22da41a56ecb9ac092585d0cc1ff0658fb9d631b
