Replace get_vanity_url function with vanity_url property on guild object.

disco/types/guild.py

@@ -357,6 +357,11 @@ class Guild(SlottedModel, Permissible):
     def owner(self):
         return self.members.get(self.owner_id)
 
+    @property
+    def vanity_url(self):
+        if self.vanity_url_code:
+            return 'https://discord.gg/' + self.vanity_url_code
+
     def get_permissions(self, member):
         """
         Get the permissions a user has in this guild.
@@ -517,9 +522,6 @@ class Guild(SlottedModel, Permissible):
     def get_invites(self):
         return self.client.api.guilds_invites_list(self.id)
 
-    def get_vanity_url(self):
-        return self.client.api.guilds_vanity_url_get(self.id)
-
     def get_emojis(self):
         return self.client.api.guilds_emojis_list(self.id)