fix(serializer):include hours in VTT timestamp formatting

Author: zubeydecivelek

cds/modules/records/serializers/vtt.py

@@ -102,5 +102,5 @@ def resize_link(frame, size):
     def time_format(seconds):
         """Helper function to convert seconds to vtt time format."""
         d = datetime.utcfromtimestamp(seconds)
-        s = d.strftime("%M:%S.%f")
+        s = d.strftime("%H:%M:%S.%f")
         return s[:-3]