Fix double sidebar header

The issue was fixed in @wordpress/interface but we were using
the older version.
The @wordpress/interface is not distributed standalone in WP Core
so we bundle it.
[MAILPOET-6371]

packages/js/email-editor/package.json

@@ -40,7 +40,7 @@
 		"@wordpress/html-entities": "^4.0.0",
 		"@wordpress/i18n": "^5.0.0",
 		"@wordpress/icons": "^10.0.0",
-		"@wordpress/interface": "^6.0.0",
+		"@wordpress/interface": "^8.2.0",
 		"@wordpress/is-shallow-equal": "^5.0.0",
 		"@wordpress/keyboard-shortcuts": "^5.0.0",
 		"@wordpress/keycodes": "^4.0.0",