Update css-fonts-4/Overview.bs

Author: xiaochengh

css-fonts-4/Overview.bs

@@ -2940,10 +2940,8 @@ The 'ascent-override', 'descent-override' and 'line-gap-override' descriptors de
 When the descriptor value is 'normal', the corresponding metric value is obtained from the
 font file directly.
 
-Note: User agents may choose different pieces of data from the font file as the metric value,
-leading to different layouts. For example, Chrome on Windows uses sTypoAscender, sTypoDescender
-and sTypoLineGap from the font's OS/2 table, while on Mac, it uses those in the HHEA table if
-available.
+Note: User agents may draw data from different places from the font file as the metric values,
+which results in different text layouts.
 
 When the descriptor value is a percentage, the corresponding metric value is resolved as the
 given percentage multiplied by the used font size. Negative values are invalid at parse time.