Require an API instance for calling send_contact

I just forgot to add the decorator in commit bef03f2.

Regression-of: bef03f2

Author: Pietro Albini

botogram/objects/mixins.py

@@ -164,6 +164,7 @@ def send_sticker(self, sticker, reply_to=None, extra=None, notify=True):
         return self._api.call("sendSticker", args, files,
                               expect=_objects().Message)
 
+    @_require_api
     def send_contact(self, phone, first_name, last_name=None, *, reply_to=None,
                      extra=None, notify=True):
         """Send a contact"""