Switch from deprecated (since Hugo 0.124) .Site.IsMultiLingual to the new hugo.IsMultilingual

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>

themes/apertis/layouts/partials/nav.html

@@ -23,7 +23,7 @@
           {{ end }}
         {{ end }}
 
-        {{ if .Site.IsMultiLingual }}
+        {{ if hugo.IsMultilingual }}
           {{ if ge (len .Site.Languages) 3 }}
             <li class="navlinks-container">
               <a class="navlinks-parent" href="javascript:void(0)">{{ i18n "languageSwitcherLabel" }}</a>
@@ -70,7 +70,7 @@
           {{ end }}
         {{ end }}
 
-        {{ if .Site.IsMultiLingual }}
+        {{ if hugo.IsMultilingual }}
           {{ if ge (len .Site.Languages) 3 }}
             <li class="navlinks-container">
               <a class="navlinks-parent" href="javascript:void(0)">{{ i18n "languageSwitcherLabel" }}</a>
@@ -148,7 +148,7 @@
           {{ end }}
         {{ end }}
 
-        {{ if .Site.IsMultiLingual }}
+        {{ if hugo.IsMultilingual }}
           {{ if ge (len .Site.Languages) 3 }}
             <li class="navlinks-container">
               <a class="navlinks-parent" href="javascript:void(0)">{{ i18n "languageSwitcherLabel" }}</a>