Rename activity group list

Author: graeme-a-stewart

calendar.md

@@ -8,7 +8,7 @@ The HSF [Community Calendar](https://calendar.google.com/calendar/embed?src=e4v3
 can be edited by people in the following Google Groups:
 
 - [HSF Steering Group](https://groups.google.com/forum/#!forum/hsf-steering)
-- [HSF Activity Area Conveners](https://groups.google.com/forum/#!forum/hsf-wg-conveners)
+- [HSF Activity Area Conveners](https://groups.google.com/forum/#!forum/hsf-activity-conveners)
 - [HSF Calendar Editors Group](https://groups.google.com/forum/#!forum/hsf-calendar-editors) Google Groups.
 
 The most straight forward way to do this is to