fix: correct the attribute for the Twitter social image (#1615)

Author: kungfux

_includes/head.html

@@ -39,7 +39,7 @@
     {%- endcapture -%}
 
     {%- capture twitter_image -%}
-      <meta property="twitter:card" content="summary_large_image" />
+      <meta name="twitter:card" content="summary_large_image" />
       <meta property="twitter:image" content="{{ img_url }}" />
     {%- endcapture -%}