Skip solid_cable gem if skip_action_cable is set (rails#52919)

This fixes the failing test
AppGeneratorTest#test_app_update_does_not_generate_action_cable_contents_when_skip_action_cable_is_given

Author: jhawthorn

railties/lib/rails/generators/rails/app/templates/Gemfile.tt

@@ -16,8 +16,10 @@ gem "tzinfo-data", platforms: %i[ <%= bundler_windows_platforms %> jruby ]
 # Use the database-backed adapters for Rails.cache, Active Job, and Action Cable
 gem "solid_cache"
 gem "solid_queue"
+<% unless options.skip_action_cable? -%>
 gem "solid_cable"
 <% end -%>
+<% end -%>
 <% if depend_on_bootsnap? -%>
 
 # Reduces boot times through caching; required in config/boot.rb