Update RSpec gem versions

[JonRowe]

No description provided.

[pirj]

Does it make sense to remove Rails 5 from the matrix? Will we still support it in rspec-rails 6?

[rspec-rails 5.x](https://github.com/rspec/rspec-rails/tree/5-0-maintenance) for Rails 6.x.
[rspec-rails 4.x](https://github.com/rspec/rspec-rails/tree/4-1-maintenance) for Rails from 5.x or 6.x.

[pirj]

The error seems to come from rack

rack-2.1.4/lib/rack/media_type.rb:18: warning: `&' interpreted as argument prefix

Wondering if this controversial commit that is both "Cleanups since master is 2.3+" and "Cleanups since master is 2.2+". The gemspec says >= 2.3.0.

[JonRowe]

@pirj the Rack one is just a warning where as the change that broke the build has a PR open to fix rails/rails#44435