[css-inline] fix typo

Author: dauwhe

css-inline-3/Overview.bs

@@ -457,7 +457,7 @@ Creating Initial Letters: the 'initial-letter' property</h3>
 
 		<dt><dfn><<integer>></dfn>
 		<dd>
-			This optional second argument argument
+			This optional second argument 
 			defines the number of lines the initial letter should sink.
 			Values less than one are invalid.
 			If omitted, it duplicates the first argument,