[css-anchor-position] Make anchor() and anchor-size() invalid outside their allowed properties. Remove related issue.

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -696,6 +696,7 @@ can use the <dfn>anchor()</dfn> function
 as a value in its [=inset properties=]
 to refer to the position of one or more [=anchor elements=].
 The ''anchor()'' function resolves to a <<length>>.
+It is only valid to be used in the [=inset properties=].
 
 <pre class=prod>
 	&lt;anchor()> = anchor( <<anchor-element>>? <<anchor-side>>, <<length-percentage>>? )
@@ -1055,10 +1056,6 @@ where this could be the case.
 		do not resolve to a [=target anchor element=],
 		the element is [=strongly hidden=].
 
-		Issue: Does misused anchor() count, like ''border-width: anchor(--foo)''?
-		I assume no, so we'll need to split out the concept of invalid usage
-		from a valid usage that fails to find an anchor.
-
 		Issue: What is a <dfn dfn for>required anchor reference</dfn>?
 		''anchor()'' functions that don't have a fallback value;
 		the default anchor *sometimes*?
@@ -1160,6 +1157,7 @@ can use the <dfn>anchor-size()</dfn> function
 in its [=sizing properties=]
 to refer to the size of one or more [=anchor elements=].
 The ''anchor-size()'' function resolves to a <<length>>.
+It is only valid to be used in the [=sizing properties=].
 
 The ''anchor-size()'' Function {#anchor-size-fn}
 ------------------------------