Remove last use of experience icons theme so we can remove it after the old...

Remove last use of experience icons theme so we can remove it after the old templates have been removed.

modules/authYubiKey/templates/yubikeylogin.twig

@@ -11,10 +11,8 @@
 
 {% block content %}
     {% if errorCode != null %}
-    <div style="border-left: 1px solid #e8e8e8; border-bottom: 1px solid #e8e8e8; background: #f5f5f5">
-        <img src="/{{ baseurlpath }}resources/icons/experience/gtk-dialog-error.48x48.png" class="float-l" style="margin: 15px;" alt="">
-        <h2>{{ '{login:error_header}'|trans }}</h2>
-        <p><span style="text-decoration: bold;">{{ errorTitle }}</p>
+    <div class="message-box error">
+        <h3>{{ errorTitle }}</h3>
         <p>{{ errorDesc }}</p>
     </div>
     {% endif %}

modules/core/templates/loginuserpass.twig

@@ -35,11 +35,6 @@
         <form class="pure-form pure-form-aligned center-form" action="?" method="post" name="f">
             <div class="form-align">
 
-                <div class="show-for-medium v-center-right">
-                    <img class="pure-img" src="/{{ baseurlpath }}resources/icons/experience/gtk-dialog-authentication.48x48.png"
-                         alt=""/>
-                </div>
-
                 <div class="pure-control-group">
                     <label for="username">{{ 'Username'|trans }}</label>
                     <input id="username" {{ forceUsername ? 'disabled="disabled"' }} placeholder="{{ username }}" type="text" name="username" class="edge"