[selectors] Mostly redundant table row dropped in <https://hg.csswg.org/drafts/rev/1b75a64dbad0> was probably a copy-paste error that was supposed to be for :user-error. Add a row for that properly.

Author: fantasai

selectors/Overview.bs

@@ -344,6 +344,11 @@ Selectors Overview</h2>
 				<td>a user-input element E that requires/does not require input
 				<td>[[#opt-pseudos]]
 				<td>3-UI/4
+			<tr>
+				<td><code>E:user-error</code>
+				<td>a user-altered user-input element E with incorrect input (invalid, out-of-range, omitted-but-required)
+				<td>[[#user-pseudos]]
+				<td>4
 		<tbody>
 			<tr>
 				<td><code>E:root</code>