Relax redis dependency

[gazorby]

Hi @tobymao, great project!

redis dependency is specified as >4.2,<4.4. Any reason why we need <4.4? Not a big deal but the readme only mention >4.2

[pahrohfit]

It was failing in a few areas, as well as tossing up lots of uncaught exceptions. I just submitted a PR(#62) a few minutes ago which includes fixes and relaxed dependency (<5.0).

[tobymao]

thanks yea, redis 4.4 broke a lot of projects with their changes to errors / cancellations.

[tobymao]

redis/redis-py#2104