Drop Python 3.7 and 3.8 support.

tox.ini

@@ -1,9 +1,9 @@
 [tox]
 envlist =
-    py{37,38,39,310}-django32
-    py{38,39,310}-django40
-    py{38,39,310,311,312}-django41
-    py{38,39,310,311,312}-django42
+    py{39,310}-django32
+    py{39,310}-django40
+    py{39,310,311,312}-django41
+    py{39,310,311,312}-django42
     py{310,311,312}-django50
     py{310,311,312,313}-django51
     lint
@@ -11,8 +11,6 @@ envlist =
 
 [gh-actions]
 python =
-    3.7: py37
-    3.8: py38
     3.9: py39
     3.10: py310
     3.11: py311