head: fix fb:app_id

_includes/head.html

@@ -21,7 +21,7 @@
  <meta name="twitter:description" content="{% if page.excerpt %}{{ page.excerpt | strip_html | strip_newlines | truncate: 160 }}{% else %}{{ site.description | nstrip_html | strip_newlines }}{% endif %}" />
  <meta name="twitter:image" content="https://gravatar.com/avatar/2bd4ed22d7f59d1a83f5a4253d74f814.jpg"/>
  <!-- Facebook -->
- <meta property="fb_app_id" content="1550553165222890" />
+ <meta property="fb:app_id" content="1550553165222890" />
  <meta name="og:title" content="{% if page.title %}{{ page.title }} — {{ site.title }}{% else %}{{ site.title }}{% endif %}" />
  <meta name="og:description" content="{% if page.excerpt %}{{ page.excerpt | strip_html | strip_newlines | truncate: 160 }}{% else %}{{ site.description | nstrip_html | strip_newlines }}{% endif %}" />
  <meta name="og:site_name" content="MikaeladDotInfo" />