channels: mark v2025pre as closed

Since Apertis v2025pre was released and according to our policy, it's time to mark v2025pre as closed.

data/channels.yaml

@@ -45,6 +45,7 @@ channels:
     release: v2025pre
     suite: v2025pre
     base: apertis/v2025pre
+    status: closed
   apertis/v2025:
     <<: &apertis_v2025
       <<: *apertis_v2024