Rename Django's dev branch to main. (#932)

More information: https://groups.google.com/g/django-developers/c/tctDuKUGosc/
Refs: django/django#14048

Author: jezdez

tox.ini

@@ -4,7 +4,7 @@ envlist =
     docs,
     py{36,37,38,39}-dj{31,30,22},
     py35-dj{22},
-    py{38,39}-djmaster,
+    py{38,39}-djmain,
 
 [gh-actions]
 python =
@@ -30,7 +30,7 @@ deps =
     dj22: Django>=2.2,<3
     dj30: Django>=3.0,<3.1
     dj31: Django>=3.1,<3.2
-    djmaster: https://github.com/django/django/archive/master.tar.gz
+    djmain: https://github.com/django/django/archive/main.tar.gz
     djangorestframework
     oauthlib>=3.1.0
     coverage
@@ -42,7 +42,7 @@ deps =
 passenv =
 	PYTEST_ADDOPTS
 
-[testenv:py{38,39}-djmaster]
+[testenv:py{38,39}-djmain]
 ignore_errors = true
 ignore_outcome = true