Update css-backgrounds-3/Overview.bs

Co-authored-by: Chris Harrelson <3453258+chrishtr@users.noreply.github.com>

Author: 2 people

css-backgrounds-3/Overview.bs

@@ -2097,7 +2097,7 @@ they apply to the top, right, bottom, and left, respectively.
 <p>Portions of the border-image that are rendered outside the border
 box do not trigger scrolling. Also such portions are invisible to mouse
 events and do not capture such events on behalf of the element, but
-they are included in the [=ink overflow area=] of the element.</p>
+but they are included in the [=ink overflow area=] of the element.</p>
 
 <p class=note>Note that, even though they never cause a scrolling
 mechanism, outset images may still be clipped by an ancestor or by the