function definedError(classMemberName) {
	return {
		messageId: "unusedPrivateClassMember",
		data: {
			classMemberName: `#${classMemberName}`,
		},
	};
}
Returns an expected error for defined-but-not-used private class member.
@param {string} classMemberName The name of the class member
@returns {Object} An expected error object