change H to lowercase to match brand

scripts/pi-hole/php/header.php

@@ -197,7 +197,7 @@
         <!-- Logo -->
         <a href="http://pi-hole.net" class="logo">
             <!-- mini logo for sidebar mini 50x50 pixels -->
-            <span class="logo-mini"><b>P</b>H</span>
+            <span class="logo-mini"><b>P</b>h</span>
             <!-- logo for regular state and mobile devices -->
             <span class="logo-lg"><b>Pi</b>-hole</span>
         </a>