rename version switcher layout file and only display if multiple permalinks

includes/header-version-switcher.html

@@ -1,5 +1,6 @@
 <!-- Versions picker that only appears in the header on homepage or product landing -->
 {% if page.relativePath == 'index.md' or page.layout == 'product-landing' or page.layout == 'product-sublanding' %}
+{% if page.permalinks and page.permalinks.length > 1 %}
 <div class="d-md-inline-block">
   <div class="border-top border-md-top-0 py-2 py-md-0 d-md-inline-block">
     <details class="dropdown-withArrow position-relative details details-reset mr-md-3 close-when-clicked-outside">
@@ -27,3 +28,4 @@
     </details>
   </div>
 {% endif %}
+{% endif %}

includes/header.html

@@ -46,8 +46,8 @@
               </details>
             </div>
 
-            <!-- Versions picker that only appears in the header on homepage/versioned homepages -->
-            {% include homepage-version-switcher %}
+            <!-- Versions picker that only appears in the header on landing pages -->
+            {% include header-version-switcher %}
 
             <div class="d-md-inline-block">