Change utt_split type to float

[RyanChimienti]

The docs show that utt_split is actually a float value, so I think this type should be changed.

I tested this change by printing out _url in abstract_sync_client.py > _handle_request(), and then making Prerecorded requests with and without this change. For utt_split values of 0.001, 2, and 1.01000, the _url was the same with and without this change.

In other words, this change seems to be a functional no-op and is just documentation.

[dvonthenen]

Yep, that's an oops. Nice catch!