Rewrite the tox.ini matrix

Thanks @felixmm!

Author: matthiask

tox.ini

@@ -3,11 +3,9 @@ envlist =
     docs
     style
     packaging
-    py{36,37}-dj{22,31,32}-sqlite
-    py{38,39}-dj{22,31,32,40,main}-sqlite
-    py{36,37,38,39}-dj{22,31,32}-{postgresql,mysql}
-    py{38,39}-dj{40,main}-{postgresql,mysql}
-    py{310}-dj{32,40,main}-{sqlite,postgresql,mysql}
+    py{36,37}-dj{22,31,32}-{sqlite,postgresql,mysql}
+    py{38,39}-dj{22,31,32,40,main}-{sqlite,postgresql,mysql}
+    py{310}-dj{40,main}-{sqlite,postgresql,mysql}
 
 [testenv]
 deps =