Perl 5.41.7 was released, update release schedule

Author: Max Maischein

Porting/release_schedule.pod

@@ -49,7 +49,7 @@ you should reset the version numbers to the next blead series.
   2024-09-20  5.41.4  ✓       Thibault Duponchelle
   2024-10-20  5.41.5  ✓       Richard Leach
   2024-11-20  5.41.6  ✓       Thibault Duponchelle
-  2024-12-20  5.41.7          Max Maischein
+  2024-12-20  5.41.7  ✓       Max Maischein
   2025-01-20  5.41.8          Steve Hay
   2025-02-20  5.41.9          Paul Evans        Contentious changes freeze
   2025-03-20  5.41.10         ?                 User-visible changes to