SpeedscopeRenderer: delete encode_speedscope_event
SpeedscopeRenderer: delete encode_speedscope_event

This commit deletes the encode_speedscope_event function because it is
no longer needed, and has been replaced with calls to json.dumps and
SpeedscopeEventEncoder.

joerick/pyinstrument,joerick/pyinstrument,joerick/pyinstrument,joerick/pyinstrument,joerick/pyinstrument,joerick/pyinstrument