Revert "[css-contain-2] Mark informative text as such"

This reverts commit dade0ab.

Author: frivoal

css-contain-2/Overview.bs

@@ -1728,7 +1728,7 @@ Description of ContentVisibilityAutoStateChangedEventInit members:
 
 </div>
 
-Note: elements in ''content-visibility: auto'' subtrees remain semantically
+Note that elements in ''content-visibility: auto'' subtrees remain semantically
 relevant even for elements that [=skip its contents=]. This means that it is
 inappropriate to use this signal to indefinitely skip DOM updates in the
 subtree that is skipped. Instead, it should be used to deprioritize updates,