[css-anchor-position-1] Change implicit anchor element example (w3c#9014)

Co-authored-by: Tab Atkins Jr <jackalmage@gmail.com>

Author: josepharhar

css-anchor-position-1/Overview.bs

@@ -160,10 +160,10 @@ a particular element is an <dfn>implicit anchor element</dfn>
 for a given positioned element.
 
 <p class=example>
-	For example, the Popover API allows a popover
-	to declare what element is anchoring it.
+	For example, the HTML spec defines an <{html-global/anchor}> attribute
+	which allows an element to declare what element it is anchored to. 
 	This makes the declared element the [=implicit anchor element=]
-	for the popover.
+	for the element with the attribute.
 
 [=Implicit anchor elements=] can be referenced
 with the ''implicit'' keyword,