Update demo header; remove Yubico logo

Author: emlun

webauthn-server-demo/src/main/webapp/img/yubico-logo.png

@@ -512,13 +512,7 @@
 <div class="base">
   <div class="content">
 
-    <div class="header-logo visible-desktop">
-      <a href="https://www.yubico.com/" title="Yubico">
-        <img src="img/yubico-logo.png"/>
-      </a>
-    </div>
-
-    <h1> Test your WebAuthn device </h1>
+    <h1> java-webauthn-server demo </h1>
 
     <form class="horizontal">
       <div class="row">