Update ID and use old API format

Author: marcoroth

_data/meetup_groups.yml

@@ -303,10 +303,10 @@
   name: Krakow Ruby Users Group (KRUG)
   service: meetupdotcom
 
-- id: krakow-ruby-users-group-2
+- id: krakow-ruby-users-group
   name: Krakow Ruby Users Group (KRUG)
   service: luma
-  ical_url: https://api2.luma.com/ics/get?entity=calendar&id=cal-EyyObsvyunM3PQP
+  ical_url: https://api.lu.ma/ics/get?entity=calendar&id=cal-EyyObsvyunM3PQP
 
 - id: krugtvm
   name: Kerala Ruby User Group