SoapboxConfig: Use cog icon instead of shield

app/soapbox/components/sidebar_menu.js

@@ -178,7 +178,7 @@ class SidebarMenu extends ImmutablePureComponent {
                 <span className='sidebar-menu-item__title'>{intl.formatMessage(messages.admin_settings)}</span>
               </a> }
               { isStaff && <NavLink className='sidebar-menu-item' to='/admin' onClick={onClose}>
-                <Icon id='shield' />
+                <Icon id='cog' />
                 <span className='sidebar-menu-item__title'>{intl.formatMessage(messages.soapbox_config)}</span>
               </NavLink> }
               <NavLink className='sidebar-menu-item' to='/settings/preferences' onClick={onClose}>

app/soapbox/features/soapbox_config/index.js

@@ -146,7 +146,7 @@ class SoapboxConfig extends ImmutablePureComponent {
     const soapbox = this.getSoapboxConfig();
 
     return (
-      <Column icon='shield' heading={intl.formatMessage(messages.heading)} backBtnSlim>
+      <Column icon='cog' heading={intl.formatMessage(messages.heading)} backBtnSlim>
         <SimpleForm onSubmit={this.handleSubmit}>
           <fieldset disabled={this.state.isLoading}>
             <FieldsGroup>