[Minor] Fix test_compose_action_spec (#2493)

Co-authored-by: Louis Faury <louis.faury@helsing.ai>

test/test_transforms.py

@@ -8694,7 +8694,7 @@ def test_compose_action_spec(self):
 
         # Final check to ensure clean sampling from the action_spec
         action = env.rand_action()
-        assert "action_2"
+        assert "action_2" in action
 
     @pytest.mark.parametrize("device", get_default_devices())
     def test_finitetensordictcheck(self, device):