update summary notes

Signed-off-by: Harshit Gangal <[email protected]>

changelog/17.0/17.0.3/summary.md

@@ -16,4 +16,7 @@ This flag enables transaction support on `StreamExecute` api.
 One enabled, VTGate `StreamExecute` grpc api will send session as the last packet in the response.
 The client should enable it only when they have made the required changes to expect such a packet.
 
-It is disabled by default.
+It is disabled by default from v17.0.3.
+
+This was a breaking change when v17.0.0 was released was causing upgrade issue for client 
+who relied on a certain behaviour of receiving streaming packets on `StreamExecute` call.