Envs doc updates: Django version, update aws.py reference in image (#24364)

- Reference correct version of Django docs
- Updates to LMS envs diagram:
    - Rename aws.py reference in image (now production.py)
    - Remove deprecated and deleted environments
- Update note on `devstack_docker.py` to explain history

lms/envs/devstack_docker.py

-""" Overrides for Docker-based devstack. """
+"""
+Left over environment file from before the transition of devstack from
+vagrant to docker was complete.
+
+This file should no longer be used, and is only around in case something
+still refers to it.
+"""
 
 from .devstack import *  # pylint: disable=wildcard-import, unused-wildcard-import

lms/envs/docs/README.rst

@@ -4,7 +4,7 @@ LMS Configuration Settings
 The lms.envs module contains project-wide settings, defined in python modules
 using the standard `Django Settings`_ mechanism.
 
-.. _Django Settings: https://docs.djangoproject.com/en/1.11/topics/settings/
+.. _Django Settings: https://docs.djangoproject.com/en/2.2/topics/settings/
 
 Different python modules are used for different setting configuration options.
 To prevent duplication of settings, modules import values from other modules,