Fix Eloquent getTimeZone method call to adhere to DateTimeInterface (#…

…16955)

Somehow the getTimeZone call in the asDateTime method is not actually
set to call the method that the DateTimeInterface defines, note the
uppercase Z on zone.

src/Illuminate/Database/Eloquent/Model.php

@@ -2979,7 +2979,7 @@ protected function asDateTime($value)
          // when checking the field. We will just return the DateTime right away.
         if ($value instanceof DateTimeInterface) {
             return new Carbon(
-                $value->format('Y-m-d H:i:s.u'), $value->getTimeZone()
+                $value->format('Y-m-d H:i:s.u'), $value->getTimezone()
             );
         }