Allow time to be shown with a header image overlay (mmistakes#1756)

Fix `read_time` logic in header image overlay

_includes/page__hero.html

@@ -45,7 +45,7 @@ <h1 id="page-title" class="page__title" itemprop="headline">
       {% if page.header.show_overlay_excerpt != false and page.excerpt %}
         <p class="page__lead">{{ page.excerpt | markdownify | remove: "<p>" | remove: "</p>" }}</p>
       {% endif %}
-      {% if site.read_time and page.read_time %}
+      {% if page.read_time %}
         <p class="page__meta"><i class="far fa-clock" aria-hidden="true"></i> {% include read-time.html %}</p>
       {% endif %}
       {% if page.header.cta_url %}