MD Settings cleanup: Remove unused paper-icon-item CSS rule.

chrome/browser/resources/settings/settings_shared_css.html

 <link rel="import" href="chrome://resources/cr_elements/shared_style_css.html">
 <link rel="import" href="settings_vars_css.html">
 
 <!-- Common styles for Material Design settings. -->
 <dom-module id="settings-shared">
   <template>
     <style include="cr-shared-style">
       :host-context([dir=rtl]) button[is='paper-icon-button-light'] {
         transform: scaleX(-1);  /* Flip on the X axis (aka mirror). */
       }
@@ skipping 188 matching lines @@
 
       /* The start (left in LTR) part (horizontally) of a list item. */
       .list-item > .start {
         flex: 1;
       }
 
       .list-item > label span[disabled] {
         opacity: var(--settings-disabled-opacity);
       }
 
-      .list-item > paper-icon-item {
-        padding: 0;
-      }
-
       /* This button has no ink ripple. */
       .list-button[is='action-link'] {
         align-items: center;
         display: flex;
         flex: 1;
         font-weight: 500;
         min-height: inherit;
       }
 
       /* A row with two lines of text. Often the lower line will be .secondary.
@@ skipping 168 matching lines @@
         transform: rotate(-135deg);
       }
 
       .column-header {
         color: var(--paper-grey-600);
         font-weight: 500;
       }
     </style>
   </template>
 </dom-module>