Move Stefan into former members

Stefan stopped contributing and participating over
12 months ago.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <[email protected]>

Author: alexellis

_data/members.yml

@@ -9,12 +9,12 @@ core:
 members:
   - alistair
   - vivek
-  - stefan
   - utsav
 
 # Listed for several months, GitHub and leaderboard shows former contributors permanently
 former_members:
   - martin
+  - stefan
 
   # - burton
   # - ed