Update schedule endpoint for preview.

Author: nikoshell

.env.preview

@@ -1,3 +1,3 @@
-EP_SESSIONS_API="https://static.europython.eu/programme/ep2024/releases/current/sessions.json"
-EP_SPEAKERS_API="https://gist.githubusercontent.com/nikoshell/24f8c99de3758dc4ed1391876c382b43/raw/bdf11fe89e5010f35dc1351e9b71c02a19adefe2/24speakers.json"
-EP_SCHEDULE_API="https://static.europython.eu/programme/ep2024/releases/current/schedule.json"
+EP_SESSIONS_API="https://static.europython.eu/programme/ep2025/releases/current/sessions.json"
+EP_SPEAKERS_API="https://static.europython.eu/programme/ep2025/releases/current/speakers.json"
+EP_SCHEDULE_API="https://static.europython.eu/programme/ep2025/releases/current/schedule.json"