How to remove span inside an element?

The following code adds and removes an "active" class to a menu (.active) It also adds a span class to the active link <span class="filet_menu"></span>.

How can I remove this span class? I've tried unwrap but it doesn't remove the span class "unwrap".

Here is my code:

$("#menu a").click(function() {
  $("#menu a").each(function() {
    $(this).removeClass("active");

    //Don't work :
    //$(this).unwrap('<span class="filet_menu"></span>');
    //$(this).contents().unwrap();
    //$('(this) > .active').unwrap();
  });
  $(this).addClass("active");
  $(this).wrapInner('<span class="filet_menu"></span>');
});

.active {
  color: #32c0ce !important;
}

.filet_menu {
  border-bottom: 2px solid #32c0ce;
  padding-bottom: 2px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<body>
  <div id="header">
    <div id="contenu_header">
      <h1>Sébastien Gicquel</h1>
      <ul id="menu">
        <li><a id="bt_diaporama" href="#diaporama">Home</a></li>
        <li><a id="bt_presentation" href="#presentation">Présentation</a></li>
        <li><a id="bt_realisations" href="#realisations">Réalisations</a></li>
        <li><a id="bt_contact" href="#contact">Contact</a></li>
      </ul>
    </div>
    <!-- fin contenu_header -->
  </div>
  <!-- fin header -->
  <div id="page">

Solution

You need to get to the contents first to unwrap. And you don't need the each loop

$("#menu a").click(function() {         
     $("#menu a.active").removeClass("active");
     $(this).addClass("active");
     $('span.filet_menu').contents().unwrap();// get previous span contents first and unwrap
     $(this).wrapInner('<span class="filet_menu"></span>');// this wraps current anchor's contents  
 });

http://jsfiddle.net/syXnH/

Or do you really need the span? why not just add/remove the classes

$("#menu a").click(function() {
    $("#menu a.active").removeClass("active filet_menu");
    $(this).addClass('filet_menu active');
});

http://jsfiddle.net/HwTNz/