Fix typo in inject_into_module test

`inject_into_module` checks `module`, not `class`.

Author: y-yagi

spec/actions/file_manipulation_spec.rb

@@ -373,7 +373,7 @@ def file
         expect(action(:inject_into_module, "application_helper.rb", ApplicationHelper, "  def help; 'help'; end\n")).to eq("      insert  application_helper.rb\n")
       end
 
-      it "does not append if class name does not match" do
+      it "does not append if module name does not match" do
         action :inject_into_module, "application_helper.rb", "App", "  def help; 'help'; end\n"
         expect(File.binread(file)).to eq("module ApplicationHelper\nend\n")
       end