[css-fonts-4] typo: miscounted number of generic font families

#2148

Author: Litherum

css-fonts-4/Overview.bs

@@ -196,7 +196,7 @@ corresponding issues of case sensitivity are described below in the
 <h4 id="generic-font-families">
 Generic font families</h4>
 
-All the generic font families must always result in at least
+Each generic font family must always result in at least
 one matched font face, for all CSS implementations. However, the
 generics may be composite faces (with different typefaces based
 on such things as the Unicode range of the character, the language of the containing