text change on outcome feature flag description

fixes CNVS-11301

test plan
* log in as a site admin
* click on account settings and go to the feature options sub-tab
* expand the arrow for the outcome gradebook flag
* verify there are no extra spaces in the text, particularly in the last sentence

Change-Id: Iaa2cedd6c5dc49483ab995e4de54f979ee975288
Reviewed-on: https://gerrit.instructure.com/30453
Reviewed-by: Braden Anderson <banderson@instructure.com>
QA-Review: Matt Fairbourn <mfairbourn@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Braden Anderson <banderson@instructure.com>