Add very tentative release date for 5.38.4/5.40.2 security releases

Author: steve-m-hay

Porting/release_schedule.pod

@@ -19,12 +19,14 @@ deemed necessary by the Steering Council.
 
   2024-06-09  5.40.0  ✓       Graham Knop
   2025-01-18  5.40.1  ✓       Steve Hay
+  2025-04-13  5.40.2          Steve Hay
 
 =head2 Perl 5.38
 
   2023-07-01  5.38.0  ✓       Ricardo Signes
   2023-11-29  5.38.2  ✓       Paul Evans
   2025-01-18  5.38.3  ✓       Steve Hay
+  2025-04-13  5.38.4          Steve Hay
 
 =head1 DEVELOPMENT RELEASE SCHEDULE