Update docs with Action Cable Redis dependency #26249
This updates the guides page with development dependencies installation for Action Cable.
Without this the following test for Action Cable fails:
bundle exec ruby -w -Itest test/subscription_adapter/redis_test.rb
I've checked the installation instructions for Arch, Ubuntu and Fedora through VirtualBox. OS X, FreeBSD and CentOS I've just searched google on how to install there.
Action Cable's test `test/subscription_adapter/redis_test.rb` fail if Redis is not installed and running. Following the guides `development_dependen there's no mention to this.
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