fixup! Revert the removal of condition

Having no condition makes it complicated to locally test against Rails
4.2

Author: pirj

example_app_generator/generate_app.rb

@@ -33,7 +33,11 @@
     gsub_file "Gemfile", /.*gem..sqlite3.*/, "gem 'sqlite3', '~> 1.3.6'"
   end
 
-  append_to_file 'Gemfile', "gem 'rails-controller-testing'\n"
+  # We soft-support Rails 4.2. `rails-controller-testing` only supports Rails 5+.
+  # This conditional is to facilitate local testing against Rails 4.2.
+  if Rails::VERSION::STRING >= '5'
+    append_to_file 'Gemfile', "gem 'rails-controller-testing'\n"
+  end
 
   if Rails::VERSION::STRING >= '6'
     gsub_file "Gemfile", /.*rails-controller-testing.*/, "gem 'rails-controller-testing', git: 'https://github.com/rails/rails-controller-testing'"