Add property to list of deduped tags (#2439)

lib/head.js

@@ -42,7 +42,7 @@ function onStateChange (head) {
   }
 }
 
-const METATYPES = ['name', 'httpEquiv', 'charSet', 'itemProp']
+const METATYPES = ['name', 'httpEquiv', 'charSet', 'itemProp', 'property']
 
 // returns a function for filtering head child elements
 // which shouldn't be duplicated, like <title/>.