[css-overflow] update abstract, fix markup

css-overflow-3/Overview.bs

@@ -14,7 +14,6 @@ Editor: Florian Rivoal, On behalf of Bloomberg, http://florian.rivoal.net/, w3ci
 Abstract: This module contains the features of CSS relating to scrollable overflow handling in visual media.
  This level is focused on completing a precise specification for the existing overflow features,
  including the 'overflow' property and its longhands;
- 'line-clamp', its longhands, and its legacy pre-standard syntax;
  and the 'text-overflow' property.
  A few additional features introduced in support of [[CSS-CONTAIN-1]] and [[CSS-CONTAIN-2]] are also defined:
  ''overflow: clip'' and the 'overflow-clip-margin' property.

css-overflow-4/Overview.bs

@@ -1170,7 +1170,7 @@ Fragmentation of Overflow: the 'continue' property</h3>
  representing the end of this <a>fragmentation container</a>.
 
 
-<h2 id="fragmentation" no-num>
+<h2 id="fragmentation" class=no-num>
 Appendix A: Redirection of Overflow</h2>
 
  <!-- Abstract: This module contains the features of CSS relating to new mechanisms of overflow handling in visual media (e.g., screen or paper). In interactive media, it describes features that allow the overflow from a fixed size container to be handled by pagination (displaying one page at a time). It also describes features, applying to all visual media, that allow the contents of an element to be spread across multiple fragments, allowing the contents to flow across multiple regions or to have different styles for different fragments. -->