Upgrade gems to support Redis 4.2

What does this MR do?

This prepares us for upgrading the redis-rb gem to 4.2+ which is required for Sidekiq 6

Related to #329430 (closed)

Upgrades

1. redis-store

   • https://github.com/redis-store/redis-store/blob/master/CHANGELOG.md#190
   • https://github.com/redis-store/redis-store/compare/v1.8.1...v1.9.0

2. redis-rack

   • https://github.com/redis-store/redis-rack/compare/v2.1.2...v2.1.3

3. rails-html-sanitizer

   • https://github.com/rails/rails-html-sanitizer/blob/master/CHANGELOG.md#142--2021-08-23
   • https://github.com/rails/rails-html-sanitizer/compare/v1.3.0...v1.4.2

4. loofah

   • https://github.com/flavorjones/loofah/blob/main/CHANGELOG.md#2120--2021-08-11
   • https://github.com/flavorjones/loofah/compare/v2.11.0...v2.12.0

rails-html-sanitizer and loofah aren't absolutely necessary but I left them in since they are tiny changes.