MD Settings: fix some dynamically bound aria-labels

chrome/browser/resources/settings/about_page/about_page.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="about_page_browser_proxy.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="../icons.html">
 <link rel="import" href="../lifetime_browser_proxy.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_page/main_page_behavior.html">
 <link rel="import" href="../settings_page/settings_animated_pages.html">
 <link rel="import" href="../settings_page/settings_section.html">
 <link rel="import" href="../settings_page_css.html">
@@ skipping 142 matching lines @@
                   [[promoteUpdaterStatus_.text]]
                   <a href="https://support.google.com/chrome/answer/95414"
                       target="_blank" id="updaterLearnMore"
                       on-tap="onLearnMoreTap_">
                     $i18n{learnMore}
                   </a>
                 </div>
                 <button class="subpage-arrow" is="paper-icon-button-light"
                     disabled="[[promoteUpdaterStatus_.disabled]]"
                     hidden="[[!promoteUpdaterStatus_.actionable]]"
-                    aria-label="[[promoteUpdaterStatus_.text]]">
+                    aria-label$="[[promoteUpdaterStatus_.text]]">
                 </button>
               </div>
             </template>
 </if>
             <div id="help" class="settings-box" on-tap="onHelpTap_" actionable>
               <div class="start">$i18n{aboutGetHelpUsingChrome}</div>
               <button class="icon-external" is="paper-icon-button-light"
                   aria-labelledby="help"></button>
             </div>
 <if expr="_google_chrome">
@@ skipping 42 matching lines @@
               <settings-detailed-build-info></settings-detailed-build-info>
             </settings-subpage>
           </template>
 </if>
         </settings-animated-pages>
       </settings-section>
     </div>
   </template>
   <script src="about_page.js"></script>
 </dom-module>