Exclude 3.13 builds from unsupported Django versions

Author: j4mie

.github/workflows/ci.yml

@@ -16,6 +16,10 @@ jobs:
             django: "5.0"
           - python: "3.9"
             django: "5.1"
+          - python: "3.13"
+            django: "4.2"
+          - python: "3.13"
+            django: "5.0"
         database_url:
           - postgres://runner:password@localhost/project
           - mysql://root:[email protected]/project