[css-anchor-position-1] Remove stray reference to legacy alignment mode

Author: fantasai

css-anchor-position-1/Overview.bs

@@ -635,8 +635,6 @@ Values other than ''position-area/none'' have the following additional effects:
 * The ''align-self/normal'' value for the [=self-alignment properties=]
 	resolves to a corresponding value, see [[#position-area-alignment]].
 * Any ''top/auto'' [=inset properties=] resolve to ''0''.
-* The box is not considered to be in a [=legacy alignment mode=]
-	in either axis.
 
 <h4 id="position-area-grid-resolution">
 Resolving the Position Area Grid</h4>