Improve load error message formatting

Author: JonRowe

lib/rspec/rails/example/system_example_group.rb

@@ -52,9 +52,9 @@ def app
           require 'action_dispatch/system_test_case'
         # rubocop:disable Lint/HandleExceptions
         rescue LoadError => e
-          p e
           # rubocop:enable Lint/HandleExceptions
           abort """
+            LoadError: #{e.message}
             System test integration requires Rails >= 5.1 and has a hard
             dependency on a webserver and `capybara`, please add capybara to
             your Gemfile and configure a webserver (e.g. `Capybara.server =