Unpin thop once onnx import is resolved

[ejm714]

In https://github.com/drivendataorg/zamba/pull/191, we pin thop to an earlier version since the latest causes an onnx import error. This is currently being discussed in issue https://github.com/Lyken17/pytorch-OpCounter/issues/173#issuecomment-1153194928. Once a new release is cut, we can unpin thop.