MD Settings: consolidate learn-more link styles

chrome/browser/resources/settings/reset_page/powerwash_dialog.html

 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="/lifetime_browser_proxy.html">
 <link rel="import" href="/reset_page/reset_browser_proxy.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-powerwash-dialog">
   <template>
     <style include="settings-shared">
-      a {
-        color: rgb(66, 133, 244);
-        text-decoration: none;
-      }
     </style>
     <dialog is="cr-dialog" id="dialog">
       <div class="title">$i18n{powerwashDialogTitle}</div>
       <div class="body">
         <span>
           $i18n{powerwashDialogExplanation}
           <a href="$i18nRaw{powerwashLearnMoreUrl}" target="_blank">
             $i18n{learnMore}
           </a>
         </span>
       </div>
       <div class="button-container">
         <paper-button class="cancel-button" on-tap="onCancelTap_"
             id="cancel">$i18n{cancel}</paper-button>
         <paper-button class="action-button" id="powerwash"
             on-tap="onRestartTap_">$i18n{powerwashDialogButton}</paper-button>
       </div>
     </dialog>
   </template>
   <script src="powerwash_dialog.js"></script>
 </dom-module>