Add python 3.8 and django30 to tox.ini and remove django111, django20 and django21 (#23889)

Add python 3.8 and django30 to tox.ini and remove django111, django20, and django21 tox environments

requirements/edx/django111.txt

@@ -1,2 +0,0 @@
-Django>=1.11,<1.12
-django-oauth-toolkit==1.1.3

requirements/edx/django20.txt

@@ -1,2 +0,0 @@
-Django>=2.0,<2.1
-django-oauth-toolkit==1.3.2

requirements/edx/django30.txt

@@ -1,3 +1,3 @@
-Django>=2.1,<2.2
+Django>=3.0,<3.1
 django-oauth-toolkit==1.3.2
 

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py{35,36,37}-django{111,20,21,22}
+envlist = py{35}-django{22},py{38}-django{22,30}
 
 # This is needed to prevent the lms, cms, and openedx packages inside the "Open
 # edX" package (defined in setup.py) from getting installed into site-packages
@@ -68,10 +68,8 @@ passenv =
     XDIST_WORKER_SUBNET
 
 deps =
-    django111: -r requirements/edx/django111.txt
-    django20: -r requirements/edx/django20.txt
-    django21: -r requirements/edx/django21.txt
     django22: -r requirements/edx/django.txt
+    django30: -r requirements/edx/django30.txt
     -r requirements/edx/testing.txt
 whitelist_externals =
     /bin/bash