Tweak Gemfile comment about Solid adapters (rails#52925)

Do not mention Action Cable if app was generated with
--skip-action-cable

Author: jeromedalbert

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

@@ -13,7 +13,11 @@ source "https://rubygems.org"
 gem "tzinfo-data", platforms: %i[ <%= bundler_windows_platforms %> jruby ]
 <% unless options.skip_solid? -%>
 
+<% if options.skip_action_cable? -%>
+# Use the database-backed adapters for Rails.cache and Active Job
+<% else -%>
 # Use the database-backed adapters for Rails.cache, Active Job, and Action Cable
+<% end -%>
 gem "solid_cache"
 gem "solid_queue"
 <% unless options.skip_action_cable? -%>