Fix index.html for Hugo 0.57.0 (#227)

In Hugo 0.57.0, a change was made that caused this theme to incorrectly render the recent posts.  More information can be found [here](gohugoio/hugoThemes#682).  This edit should fix that error.  It has been tested on a live site and it works.

layouts/partials/recent_posts.html

@@ -15,8 +15,7 @@ <h2>{{ .Site.Params.recent_posts.title }}</h2>
             <!-- *** BLOG HOMEPAGE *** -->
 
             <div class="row">
-
-                {{ $posts := .Paginate (where .Site.RegularPages "Type" "blog") }}
+                {{ $posts := .Paginate (where site.RegularPages "Type" "in" site.Params.mainSections) }}
                 {{ range first 4 $posts.Pages }}
                 <div class="col-md-3 col-sm-6">
                     <div class="box-image-text blog">