Remove "Application" section title from routes

This PR standardizes the output of the HTML and console based routes to not include the title for "Application Routes" those that are defined by the application. Instead only routes defined in engines get any special treatment. 

Based on this conversation:

https://github.com/rails/rails/commit/af5c0fd85fce1adb311083dd1ecf96432ee8caa3#commitcomment-2458823

ATP actionpack /cc @carlosantoniodasilva