use AdminLTE function to toggle dropdown-menu

AdminLTE has already an implemented function to toggle the user menu.
So there is no need to use an own script in footer.js
 
Benefit: The dropdown-menu closes if you click on a blank Place

scripts/pi-hole/php/header.php

@@ -234,8 +234,8 @@ if($auth) {
             <div class="navbar-custom-menu">
                 <ul class="nav navbar-nav">
                     <!-- User Account: style can be found in dropdown.less -->
-                    <li id="dropdown-menu" class="dropdown user user-menu">
-                        <a href="#" class="dropdown-toggle">
+                    <li class="dropdown user user-menu">
+                        <a href="#" class="dropdown-toggle" data-toggle="dropdown" aria-expanded="true">
                             <img src="img/logo.svg" class="user-image" style="border-radius: initial" sizes="160x160" alt="Pi-hole logo" />
                             <span class="hidden-xs">Pi-hole</span>
                         </a>