Fix the python version for django51

Author: ArtyomVancyan

.github/workflows/tests.yml

@@ -45,12 +45,12 @@ jobs:
           - python: "3.11"
             env: py311-django42
 
-          - python: "3.9"
-            env: py39-django51
           - python: "3.10"
             env: py310-django51
           - python: "3.11"
             env: py311-django51
+          - python: "3.12"
+            env: py312-django51
 
           - python: "3.10"
             env: py310-django52