OOBE - Change initial focus to "Lets go" button

The initial focus on the OOBE 'Welcome' screen has been changed from
the language button to the "Let's go" button as per UX request.

Fixed: 992434
Change-Id: Iff2917c74c8463ebe1f3163bcb61e802cbbcf0e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1991442
Commit-Queue: Renato Silva <rrsilva@google.com>
Commit-Queue: Denis Kuznetsov [CET] <antrim@chromium.org>
Auto-Submit: Renato Silva <rrsilva@google.com>
Reviewed-by: Denis Kuznetsov [CET] <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729394}

chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js

@@ -328,7 +328,7 @@
      * This is stored ID of currently focused element to restore id on returns
      * to this dialog from Language / Timezone Selection dialogs.
      */
-    focusedElement_: 'languageSelectionButton',
+    focusedElement_: 'welcomeNextButton',
 
     onLanguageClicked_: function() {
       this.focusedElement_ = 'languageSelectionButton';