[css-2020] Tweak wording

Author: fantasai

css-2020/Overview.bs

@@ -367,8 +367,8 @@ Fairly Stable Modules with limited implementation experience</h3>
 <h3 id=rough-interop>
 Modules with Rough Interoperability</h3>
 
-	The following modules are widely deployed with <a>rough interoperability</a>,
-	but the details are not fully worked out or sufficiently well-specified
+	Although the following modules have been widely deployed with <a>rough interoperability</a>,
+	their details are not fully worked out or sufficiently well-specified
 	and they need more testing and bugfixing.
 	We hope to incorporate them into the [[#css|official definition of CSS]] in a future snapshot.