Remove H2 as it is not important to site structure (mmistakes#3012)

This should not use a H2, as that is not an important headline, and thus a H2 here would probably hurt in page SEO.

Author: lsolesen

_includes/skip-links.html

@@ -1,5 +1,4 @@
 <nav class="skip-links">
-  <h2 class="screen-reader-text">{{ site.data.ui-text[site.locale].skip_links | default: 'Skip links' }}</h2>
   <ul>
     <li><a href="#site-nav" class="screen-reader-shortcut">{{ site.data.ui-text[site.locale].skip_primary_nav | default: 'Skip to primary navigation' }}</a></li>
     <li><a href="#main" class="screen-reader-shortcut">{{ site.data.ui-text[site.locale].skip_content | default: 'Skip to content' }}</a></li>