container: fix warning for cls_has_array_context_attr #71

Job	Run time
Mypy	1m 55s
Documentation	2m 13s
Tests for downstream project meshmode	12m 58s
Examples Conda Py3	1m 44s
Tests for downstream project grudge	10m 38s
Pylint	1m 58s
Tests for downstream project mirgecom	4s
Pytest Conda Py3 Intel	2m 26s
Tests for downstream project mirgecom_examples	4s
Pytest Conda Py3 POCL	2m 37s
Ruff	8s
	36m 45s

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