Update supervision icon to the latest version

BEFORE: http://screenshot/pUOjJiTuqw7.png
AFTER: http://screenshot/bgRxAxYz5M6.png

Bug: 1021994
Change-Id: I3abf24d71335e4fa38d1cb12b201122af4391df8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1900276Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Felipe Cerqueira <cerqueira@google.com>
Cr-Commit-Position: refs/heads/master@{#713156}

chrome/browser/resources/chromeos/login/oobe_supervision_transition.css

@@ -11,3 +11,8 @@ paper-progress {
   padding: 40px 0 0 0;
   width: 100%;
 }
+
+.supervision-icon {
+  --iron-icon-height: 32px;
+  --iron-icon-width: 32px;
+}

chrome/browser/resources/chromeos/login/oobe_supervision_transition.html

@@ -10,7 +10,7 @@
     <oobe-dialog id="supervisionTransitionDialog" role="alert"
         aria-label$="[[getDialogA11yTitle_(locale, isRemovingSupervision_)]]">
       <iron-icon src="chrome://oobe/supervision_icon.png" slot="oobe-icon"
-          aria-hidden="true">
+          class="supervision-icon" aria-hidden="true">
       </iron-icon>
       <h1 slot="title" id="supervisionTitle">
         <div hidden="[[isRemovingSupervision_]]">