[MD settings] touch up sub-page titles and icons

chrome/browser/resources/settings/settings_shared_css.html

 <!-- Common styles for Material Design settings. -->
 <dom-module id="settings-shared">
   <template>
     <style>
       :root {
         --checkbox-margin-start: 2px;
         --checkbox-size: 16px;
         --checkbox-spacing: 18px;
         --iron-icon-fill-color: var(--paper-grey-500);
         --iron-icon-height: 20px;
-        --iron-icon-stroke-color: var(--paper-grey-500);
         --iron-icon-width: 20px;
         --paper-icon-button: {
           width: 36px;
           height: 36px;
         }
         --settings-background-color: var(--paper-blue-grey-50);
         --settings-secondary: {
           color: var(--paper-grey-500);
           font-weight: 400;
         }
@@ skipping 11 matching lines @@
         display: flex;
         font-size: 100%;
         font-weight: 500;
         margin: 0;
         min-height: 40px;
       }
 
       iron-icon[icon=check],
       iron-icon[icon=done] {
        --iron-icon-fill-color: var(--google-green-500);
-       --iron-icon-stroke-color: var(--google-green-500);
       }
 
       paper-button {
         margin: 0;
         min-width: auto;
       }
 
       paper-button[toggles][active] {
         background-color: var(--paper-grey-300);
       }
@@ skipping 190 matching lines @@
 
       .settings-checkbox-spacer {
         -webkit-margin-start: calc(
             var(--checkbox-margin-start) +
             var(--checkbox-size) +
             var(--checkbox-spacing));
       }
     </style>
   </template>
 </dom-module>