[tests] Added missing fixture in test_unitxt_tasks.py (#3163)

* Added missing fixture in test_unitxt_tasks.py

* pacify pre-commit

---------
Co-authored-by: Baber Abbasi <92168766+baberabb@users.noreply.github.com>

tests/test_unitxt_tasks.py

@@ -7,6 +7,11 @@ from lm_eval.api.task import ConfigurableTask
 from tests.test_tasks import BaseTasks, task_class
 
 
+@pytest.fixture()
+def limit() -> int:
+    return 10
+
+
 @pytest.mark.parametrize(
     "task_class",
     task_class(