OOBE a11y: mark sync consent images as aria-hidden

Fixed: 1133776
Change-Id: I45a1a077fa76de40a1c5b7602e7382c8335acdd9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2479424
Commit-Queue: Denis Kuznetsov [CET] <antrim@chromium.org>
Auto-Submit: Denis Kuznetsov [CET] <antrim@chromium.org>
Reviewed-by: Thomas Tellier <tellier@google.com>
Cr-Commit-Position: refs/heads/master@{#817940}

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

@@ -89,7 +89,8 @@
 
         <!-- "Chrome OS settings sync" -->
         <div class="overview-list-item layout horizontal center">
-          <img class="overview-list-item-icon" src="images/settings_gear.svg" width="24" height="24">
+          <img class="overview-list-item-icon" src="images/settings_gear.svg"
+              width="24" height="24" aria-hidden="true">
           <div class="flex layout vertical center-justified">
             <div role="heading" aria-level="2" class="overview-list-item-title" id="osSyncName" consent-description>
               [[i18nDynamic(locale, 'syncConsentScreenOsSyncName')]]
@@ -102,7 +103,8 @@
 
         <!-- "Chrome browser sync" -->
         <div class="overview-list-item layout horizontal center">
-          <img class="overview-list-item-icon" src="images/browser_sync.svg" width="24" height="24">
+          <img class="overview-list-item-icon" src="images/browser_sync.svg"
+              width="24" height="24" aria-hidden="true">
           <div class="flex layout vertical center-justified">
             <div role="heading" aria-level="2" class="overview-list-item-title" consent-description
               id="browserSyncName">