Swiss Python Summit CFP extension (#85)

* Swiss Python Summit CFP extension

* Update conferences.yml

---------

Co-authored-by: Jesper Dramsch <[email protected]>

Author: systematicguy

_data/conferences.yml

@@ -283,6 +283,7 @@
   link: https://python-summit.ch/
   cfp_link: https://talks.python-summit.ch/sps25/cfp
   cfp: '2025-05-31 23:59:00'
+  cfp_ext: '2025-06-15 23:59:00'
   timezone: Europe/Zurich
   place: Rapperswil, Switzerland
   start: 2025-10-16