Update rate limit

[RFBomb]

Reduce the sleep timer from 2s to 650ms, in accordance with updated (higher) rate limits allowed as of 7/1. Replace all 'sleep()' timers with the new function that uses the calculated rate limit time.

• If implementing this change prior to 7/1, the variable must be changed to 1050ms to stay within the 60/min range in effect until 7/1

[andrewbanchich]

Looks like there's a build failure due to needing to import debug!.

[andrewbanchich]

Thanks!