Add DATA sub to Swiss Python Summit

Author: systematicguy

_data/conferences.yml

@@ -237,7 +237,7 @@
   end: 2025-10-17
   sponsor: https://www.python-summit.ch/sponsoring/
   twitter: pythonsummit
-  sub: PY
+  sub: PY,DATA
   note: 'Day 1: General Language Topics; Day 2: Data Science Topics'
   location:
   - title: Swiss Python Summit 2025