update sis documentation don't recommend bad stuff
update sis documentation don't recommend bad stuff

test plan
 - rake doc:api should work

fixes VICE-1219
flag = none

Change-Id: I701f2abb662857bb4ce6da1849e2dac52327d146
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/260580
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Caleb Guanzon <54fa1f30d451e4f3c341a8f3c47c9215fd0be9c6@instructure.com>
Reviewed-by: Davis Hyer <60fbffed049dcae9186e63e354cbc0b825bf5523@instructure.com>
QA-Review: Caleb Guanzon <54fa1f30d451e4f3c341a8f3c47c9215fd0be9c6@instructure.com>
QA-Review: Davis Hyer <60fbffed049dcae9186e63e354cbc0b825bf5523@instructure.com>
Product-Review: Caleb Guanzon <54fa1f30d451e4f3c341a8f3c47c9215fd0be9c6@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms