How to fix «Element 'item': This element is not expected» after upgrading Magento to 2.2?

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I had the following invalid code block in a custom design theme:

<referenceBlock name="header-wrapper">
	<item name="authentication" xsi:type="array">
		<item name="sortOrder" xsi:type="string">1</item>
		<item name="component" xsi:type="string">Magento_Checkout/js/view/authentication</item>
		<item name="displayArea" xsi:type="string">authentication</item>
		<item name="children" xsi:type="array">
			<item name="errors" xsi:type="array">
				<item name="sortOrder" xsi:type="string">0</item>
				<item name="component" xsi:type="string">Magento_Checkout/js/view/authentication-messages</item>
				<item name="displayArea" xsi:type="string">messages</item>
			</item>
		</item>
	</item>
</referenceBlock>

I have just deleted it.