Users: Add `LIMIT 1` to SQL query in `WP_User::get_data_by()`, as only one row is requested.

Props spacedmonkey.
Fixes #43692.

git-svn-id: https://develop.svn.wordpress.org/trunk@43651 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-user.php

@@ -240,7 +240,7 @@ class WP_User {
 
 		if ( ! $user = $wpdb->get_row(
 			$wpdb->prepare(
-				"SELECT * FROM $wpdb->users WHERE $db_field = %s",
+				"SELECT * FROM $wpdb->users WHERE $db_field = %s LIMIT 1",
 				$value
 			)
 		) ) {