Move finish_template as the last public method in the generator

This moves the [recently added](https://github.com/rails/rails/commit/84e261b9309d362a210ed55941f2852ec4230038) `delete_js_folder_skipping_javascript` method before `finish_template` which should be the last public method defined. This ensures a less misleading execution order in the generator.

I discovered this by reading through [thoughtbot/suspenders](https://github.com/thoughtbot/suspenders/blob/master/lib/suspenders/generators/app_generator.rb#L18-21) code, which 

PS: I'm fairly new to Rails source code and enjoying digging it :heart: