fix(html): bad value for height

Error: Bad value auto for attribute height on element img: Expected a digit but saw a instead.
Source: Nu Html Checker

Author: Rotzbua

_includes/nav.html

@@ -61,7 +61,7 @@
   <div id="navbar-mobile" class="overlay">
     <button class="closebtn" onclick="closeNav()">&times;</button>
       <div class="overlay-header">
-        <img src="/assets/branding/logo-icon.svg" width="80" height="auto"
+        <img src="/assets/branding/logo-icon.svg" width="80"
              alt="{% t generic.accessibility.logo %}" />
       </div>
       <div class="overlay-content">