layouts/partials/recent.html: Only list "Regular" pages

This makes Hugo only list "Regular" pages in the sidebar. Otherwise
if you have very few posts, for example, you might see one entry in
the list called "Posts".

See: https://gohugo.io/functions/where/#mainsections

layouts/partials/recent.html

@@ -2,7 +2,7 @@
     <h4>{{ i18n "recentPosts" }}</h4>
     <ol class="list-unstyled">
 {{ $num_recent_posts := (index .Site.Params.sidebar "num_recent_posts" | default 5) }}
-{{ range first $num_recent_posts (where .Site.Pages "Section" "in" .Site.Params.mainSections) }}
+{{ range first $num_recent_posts (where .Site.RegularPages "Section" "in" .Site.Params.mainSections) }}
 <li><a href="{{.RelPermalink}}">{{.Title | markdownify }}</a></li>
 {{ end }}
     </ol>