Upgrade heroku tiers for wagtail and django apps

[xmedr]

Overview

This is a quick change to update the dyno and postgres tiers for new wagtail/django apps made in cookiecutter

• Closes #351

Demo

These changes applied to a parserator review app:

Testing Instructions

• These changes were already applied to a review app in parserator
  • The pr can be found here
  • The review app can be messed with here
• Confirm that the settings on heroku look correct
• Confirm that the app works as normal