Additional updates for compatibility with tox 4

'[tox] skipsdist' behaves differently in tox 4 [1]. In addition, setting
'[testenv] basepython' with '[tox] ignore_basepython_conflict' has been
the cause of a few tox 4 bugs (most since fixed, thankfully) and might
be deprecated [2]. Remove it since we don't need it in any of our
environments.

[1] tox-dev/tox#2730
[2] tox-dev/tox#2846

Conflicts:
	tox.ini

NOTE(stephenfin): Conflicts are due to lack of support for Django 4.1.

Signed-off-by: Stephen Finucane <stephen@that.guru>
(cherry picked from commit a03a0a5)

tox.ini

@@ -1,11 +1,9 @@
 [tox]
 minversion = 3.2
 envlist = pep8,docs,py{37,38,39}-django32,py{38,39,310}-django{40}
-skipsdist = true
-ignore_basepython_conflict = true
 
 [testenv]
-basepython = python3
+skip_install = true
 deps =
     -r{toxinidir}/requirements-test.txt
     django32: django~=3.2.0