python: remove converter->metadata dependency
python: remove converter->metadata dependency

Summary: it's unused left over from a previous iteration

Reviewed By: nanshu

Differential Revision: D36427670

fbshipit-source-id: e61e956960056760e90c4659b569da5f1e6763c3

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift