[css-anchor-position] Remove lingering extra definition of the position fallback origin

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -1623,7 +1623,6 @@ These modified styles are applied to the element via [=interleaving=],
 so they affect [=computed values=]
 (and can trigger transitions/etc)
 even tho they depend on layout and [=used values=].
-They are applied as part of the [=position fallback origin=].
 
 <div algorithm>
 	To <dfn>apply a position option</dfn> to an element |el|,