[css-syntax] Typo fix

Author: SimonSapin

css-syntax/Overview.bs

@@ -3272,7 +3272,7 @@ Serialization</h2>
 
 	This specification does not define how to serialize CSS in general,
 	leaving that task to the CSSOM and individual feature specifications.
-	In particular, the serialization of comments an whitespace is not defined.
+	In particular, the serialization of comments and whitespace is not defined.
 
 	The only requirement for serialization is that it must "round-trip" with parsing,
 	that is, parsing the stylesheet must produce the same data structures as