tests: use session-scoped exp celery fixtures when possible

tests/unit/repo/experiments/queue/test_celery.py

@@ -49,10 +49,10 @@ def test_shutdown_with_kill(test_queue, mocker):
     )
 
 
-def test_post_run_after_kill(test_queue):
+def test_post_run_after_kill(session_queue):
     from celery import chain
 
-    sig_bar = test_queue.proc.run_signature(
+    sig_bar = session_queue.proc.run_signature(
         ["python3", "-c", "import time; time.sleep(10)"], name="bar"
     )
     sig_bar.freeze()
@@ -65,7 +65,7 @@ def test_post_run_after_kill(test_queue):
 
     while True:
         try:
-            test_queue.proc.kill("bar")
+            session_queue.proc.kill("bar")
             assert result_foo.status == "PENDING"
             break
         except ProcessLookupError: