Pin redis<4.0 on M1 Macs

[wuisawesome]

Why are these changes needed?

This PR pins redis on M1 macs. Redis 4.0+ adds extra warning messages if hiredis is not installed, but hiredis doesn't provide m1 mac wheels, which makes it difficult to install.

Related issue number

Checks

• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[pcmoritz]

4.0.1 was just released that should remove the warning: redis/redis-py#1721

Can you try if that fixes it? It would be preferable not to pin :)

https://github.com/redis/redis-py/releases/tag/v4.0.1

[wuisawesome]

Just tested and I still get the error message. (it comes from this line: https://github.com/redis/redis-py/blob/4e9cc015e32ef305429ff9dfa200e28dd63e6663/redis/connection.py#L71)

[wuisawesome]

That being said, if Redis intends to remove the error message, maybe we don't need to merge this PR, and we can just wait for them to fix it upstream?

[wuisawesome]

Let me close this for now and see if redis/redis-py#1726 gets accepted.