Settings WebUI: Fix multidevice radio buttons focus

With crrev.com/650435, focus and other accessibility attributes were
moved to the radio button itself instead of the host element.

Change-Id: I42cf86b2ea4bb67cb55add00dc6602e692a8800c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1706909Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Commit-Queue: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678404}

chrome/browser/resources/settings/multidevice_page/multidevice_radio_button.html

@@ -30,7 +30,15 @@
       }
     </style>
 
-    <div class="disc-wrapper">
+    <div
+        aria-checked$="[[getAriaChecked_(checked)]]"
+        aria-disabled$="[[getAriaDisabled_(disabled)]]"
+        aria-labelledby="labelWrapper"
+        class="disc-wrapper"
+        id="button"
+        role="radio"
+        tabindex="0"
+        on-keydown="onInputKeydown_">
       <div class="disc-border"></div>
       <div class="disc"></div>
     </div>