JS: Use arrow functions

All function () {} left in the code reference `this` and thus couldn't use arrow functions.

adminer/schema.inc.php

@@ -52,7 +52,7 @@ foreach (table_status('', true) as $table => $table_status) {
 ?>
 <div id="schema" style="height: <?php echo $top; ?>em;">
 <script<?php echo nonce(); ?>>
-qs('#schema').onselectstart = function () { return false; };
+qs('#schema').onselectstart = () => false;
 const tablePos = {<?php echo implode(",", $table_pos_js) . "\n"; ?>};
 const em = qs('#schema').offsetHeight / <?php echo $top; ?>;
 document.onmousemove = schemaMousemove;