Fix "character class has duplicated range" warning

This fixes the following warning when running
`railties/test/generators/plugin_generator_test.rb`:

  ```
  warning: character class has duplicated range
  ```

railties/test/generators/plugin_generator_test.rb

@@ -412,7 +412,7 @@ def test_create_mountable_application_with_mountable_option_and_hypenated_and_un
     assert_file "my_hyphenated-name/app/helpers/my_hyphenated/name/application_helper.rb",         /module MyHyphenated\n  module Name\n    module ApplicationHelper\n    end\n  end\nend/
     assert_file "my_hyphenated-name/app/views/layouts/my_hyphenated/name/application.html.erb" do |contents|
       assert_match "<title>My hyphenated name</title>", contents
-      assert_match(/stylesheet_link_tag\s+[""]my_hyphenated\/name\/application['"]/, contents)
+      assert_match(/stylesheet_link_tag\s+['"]my_hyphenated\/name\/application['"]/, contents)
       assert_no_match(/javascript_include_tag\s+['"]my_hyphenated\/name\/application['"]/, contents)
     end
   end