There is not an easy way to stop the "by the way" in the settings but there is a work-around. To create a routine to stop the "by the way" give the following a try.
1. open the Alexa app and select “Routines” from the “more” menu in the lower right.
2. Press the “+” button in the top right to create a new routine.
3. Create name for the routine name
4. select “Schedule” from the “When this happens” menu.
5. Pick a time for the routine to run every day and press next to return to the main routine screen.
6. tap “Add action”
7. select the “Custom” option at the top.
8. enter “stop by the way” into the text field,
9. select “Next” in the upper right
10. select “Save” in the upper right to finish creating your new routine.
Whenever the routine runs, alexa will say "Okay, I will snooze my suggestions for now"