reduce test matrix

Author: snopoke

.github/workflows/tests.yml

@@ -26,9 +26,11 @@ jobs:
           - "3.10"
           - "3.11"
           - "3.12"
-        celery-version:
-          - ">=5.3,<5.4"
-          - ">=5.4"
+        include:
+          - celery-version: ">=5.3,<5.4"
+            python-version: "3.12"
+          - celery-version: ">=5.4"
+            python-version: "3.12"
     steps:
       - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}