[css-scrollbars] Adjust abstract

Impact on layout is in css-overflow after all.

Author: frivoal

css-scrollbars-1/Overview.bs

@@ -15,7 +15,7 @@ Editor: Rossen Atanassov, Microsoft, ratan@microsoft.com, w3cid 49885
 Editor: Florian Rivoal, Invited Expert, https://florian.rivoal.net/, w3cid 43241
 Abstract: This CSS module defines properties
           to influence the visual styling of scrollbars,
-          introducing controls for their color, width, and impact on layout.
+          introducing controls for their color and width.
 Link Defaults: css-color-3 (property) color
 </pre>