[DOC] Fix grep_v description

Author: vinc

enum.c

@@ -5033,7 +5033,7 @@ enum_compact(VALUE obj)
  * - #flat_map (aliased as #collect_concat): Returns flattened objects returned by the block.
  * - #grep: Returns elements selected by a given object
  *   or objects returned by a given block.
- * - #grep_v: Returns elements selected by a given object
+ * - #grep_v: Returns elements not selected by a given object
  *   or objects returned by a given block.
  * - #inject (aliased as #reduce): Returns the object formed by combining all elements.
  * - #sum: Returns the sum of the elements, using method <tt>+</tt>.