remove duplicated < in css-properties-values-api (w3c#419)

remove duplicated < in css-properties-values-api

Author: hwanseung

css-properties-values-api/Overview.bs

@@ -424,7 +424,7 @@ computed value is as specified. Calc expressions that are
 <number> and <percentage> values get reduced during computation to simple
 numbers and percentages respectively.
 
-For <<transform-function> values contained in <transform-list> values,
+For <transform-function> values contained in <transform-list> values,
 the computed value is as specified but with all lengths resolved to their
 computed values.