Improve and fix Redis documentation

[mzbroch]

Documentation about Redis is not up to date and can cause confusion.
Specifically elements related to Redis config in nautobot_config.py would better fit under Nautobot docs too.

[ubajze]

Hey @mzbroch, is this the doc you are referring to: https://docs.nautobot.com/projects/helm-charts/en/stable/advanced-features/redis-sentinel/