Update PyData Helsinki link to new URL (#12)

Author: jkseppan

index.md

@@ -155,7 +155,7 @@ can approach one of the organisers directly or email
 - Our friends at [Archipylago](https://archipylago.dev/) down the road in Turku host
   monthly meetups and sprints for Python people.
 
-- The [PyData Helsinki](https://pydata-helsinki.github.io/) arranges data and machine-learning focused Python meetups in Helsinki.
+- The [PyData Helsinki](https://pydata-helsinki.fi/) arranges data and machine-learning focused Python meetups in Helsinki.
 
 - [PyLadies Tampere](https://www.linkedin.com/company/pyladies-tampere/) is a
   mentorship group focused on helping more women become active participants and