Substack subscriber importer: add translation function (#96348)

client/my-sites/importer/newsletter/subscribers/paid-subscribers/success-notice.tsx

@@ -1,15 +1,20 @@
 import { Notice } from '@wordpress/components';
 import { createInterpolateElement } from '@wordpress/element';
 import { sprintf } from '@wordpress/i18n';
+import { useI18n } from '@wordpress/react-i18n';
 
 export default function SuccessNotice( { allEmailsCount }: { allEmailsCount: number } ) {
+	const { _n } = useI18n();
 	return (
 		<Notice status="success" className="importer__notice" isDismissible={ false }>
 			{ createInterpolateElement(
 				sprintf(
-					// @TODO: add _n() translation function once we finalize this copy.
 					// translators: %d is the number of subscribers
-					'All set! We’ve found <strong>%d subscribers</strong> to import.',
+					_n(
+						'All set! We’ve found <strong>%d subscriber</strong> to import.',
+						'All set! We’ve found <strong>%d subscribers</strong> to import.',
+						allEmailsCount
+					),
 					allEmailsCount
 				),
 				{