Remove buggy conditional around related posts header (mmistakes#901)

This removes a buggy conditional that checks if `related_label` is
available in translations before displaying the header for related
posts but this header already handle missing translation by using a
default string.

With this fix the header is displayed even if the translation for this
label isn't available.

Fix mmistakes#900

_layouts/single.html

@@ -63,9 +63,7 @@ <h4 class="page__meta-title">{{ site.data.ui-text[site.locale].meta_label }}</h4
   {% comment %}<!-- only show related on a post page when not disabled -->{% endcomment %}
   {% if page.id and page.related and site.related_posts.size > 0 %}
     <div class="page__related">
-      {% if site.data.ui-text[site.locale].related_label %}
-        <h4 class="page__related-title">{{ site.data.ui-text[site.locale].related_label | default: "You May Also Enjoy" }}</h4>
-      {% endif %}
+      <h4 class="page__related-title">{{ site.data.ui-text[site.locale].related_label | default: "You May Also Enjoy" }}</h4>
       <div class="grid__wrapper">
         {% for post in site.related_posts limit:4 %}
           {% include archive-single.html type="grid" %}