[css-gcpm-4][editorial] fix markup

Author: tabatkins

css-gcpm-4/Overview.bs

@@ -54,7 +54,7 @@ Headers often contain document content, and it is desirable to both display that
 
 
 <pre class="propdef">
-Name: <dfn id="copy-into-property">copy-into</dfn>
+Name: copy-into
 Value: none |  [ [ &lt;custom-ident>  &lt;content-level>] [,  &lt;custom-ident>  &lt;content-level>]*  ]?
 Initial: none
 Applies To: all elements and pseudo-elements, but not ::first-line or ::first-letter.