[css-inline-3] Remove implementation warning, now that inheritance/propagation has been more fully worked out.

Author: fantasai

css-inline-3/Overview.bs

@@ -1276,15 +1276,6 @@ Calculating the Logical Height Contributions (“Layout Bounds”) of Inline Box
 <h2 id="leading-trim">
 Trimming Leading Over/Under Text</h2>
 
-	ISSUE: This is a draft of a proposal,
-	and may change significantly
-	as design critiques and use cases are registered.
-	Values and property names may be added, dropped, and/or renamed,
-	and the overall syntax or behavior may change,
-	particularly in response to authoring and robustness considerations
-	for handling descendant boxes.
-	<strong>Do not ship (yet).</strong>
-
 	To ensure consistent spacing in the basic case of running text,
 	CSS line layout introduces leading both above and below
 	the text content of each line