Fix typo in scroll.asciidoc

Fix scroll request with sort.

Closes #15493

docs/reference/search/request/scroll.asciidoc

@@ -98,7 +98,7 @@ curl -XGET 'localhost:9200/_search?scroll=1m' -d '
 {
   "sort": [
     "_doc"
-  }
+  ]
 }
 '
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