APIchanges: Add entry for AV_PKT_DATA_RTCP_SR

doc/APIchanges

@@ -2,6 +2,9 @@ The last version increases of all libraries were on 2025-03-28
 
 API changes, most recent first:
 
+2025-07-07 - eca477da52 - lavc 62.6.100 - packet.h
+  Add AV_PKT_DATA_RTCP_SR.
+
 2025-07-01 - 39d5a998bd - lavc 62.4.101 - packet.h
   Add AV_PKT_DATA_3D_REFERENCE_DISPLAYS.