add 5.41.13 to release history

..and mark 5.42.0 as unknown

Author: karenetheridge

Porting/release_schedule.pod

@@ -59,7 +59,8 @@ you should reset the version numbers to the next blead series.
                                                 programs freeze
   2025-04-20  5.41.11 ✓       Karen Etheridge   Full program freeze
   2025-04-21  5.41.12 ✓       Karen Etheridge
-  2025-05-20  5.42.0          ?                 New perl!
+  2025-05-28  5.41.13 ✓       Philippe Bruhat
+  2025-0?-??  5.42.0          ?                 New perl!
 
 =head1 VICTIMS