[css-anchor-position] Use 'part-like pseudo' as the requirement.

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -376,12 +376,8 @@ or nothing (a missing specifier).
 		is either not [=absolutely positioned=]
 		or precedes |query el| in the tree order.
 
-	* |el| is either an [=element=],
-		or a [=pseudo-element=] that acts like one.
-
-		Issue: define the term that actually means this,
-		matching ::before/after/backdrop/etc
-		(but not ::marker/placeholder/etc whose box is not detectable).
+	* |el| is either an [=element=]
+		or a [=part-like pseudo-element=].
 
 	* |el| is not in the [=skipped contents=] of another element.
 </div>