Bug Fix: In `NextId.reset()`, reset all Redis masters
Previously, I'd modified the `NextId.__current_id` getter to get the ID from `n // 2 + 1` Redis masters, then to return the highest of those
IDs.
This means that `NextId.reset()` must delete the Redis key from all masters.
What's Changed
* In NextId.reset(), reset all Redis masters by brainix in https://github.com/brainix/pottery/pull/463
**Full Changelog**: https://github.com/brainix/pottery/compare/v1.4.1...v1.4.2