Fix accessibility label ID mismatch

Refs https://chromium-review.googlesource.com/c/chromium/src/+/2231678.

When the label was updated to use underscores, the associated jQuery
call in accessibility.js was not likewise updated, so it would error
with:

"Uncaught TypeError: Cannot read property 'value' of null"

Change-Id: Iac01a1246a0bb1e0bb8a7c02a5965cfba5f66323
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2296883Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Abigail Klein <abigailbklein@google.com>
Commit-Queue: Abigail Klein <abigailbklein@google.com>
Cr-Commit-Position: refs/heads/master@{#788770}

chrome/browser/resources/accessibility/accessibility.js

@@ -80,7 +80,7 @@ cr.define('accessibility', function() {
     // function with the result.
     const requestType = element.id.split(':')[1];
     if (data.type == 'browser') {
-      const delay = $('native_ui_delay').value;
+      const delay = $('native-ui-delay').value;
       setTimeout(() => {
         chrome.send(
             'requestNativeUITree', [{