Fix call-seq of lazy.filter_map [ci skip]

enumerator.c

@@ -2038,12 +2038,11 @@ lazy_filter_map_proc(RB_BLOCK_CALL_FUNC_ARGLIST(val, m))
 
 /*
  *  call-seq:
- *     enum.filter_map { |obj| block } -> an_enumerator
- *     enum.filter_map                 -> an_enumerator
+ *     lazy.filter_map { |obj| block } -> lazy_enumerator
  *
  *  Returns an enumerator which will return a new array containing the
  *  truthy results (everything except +false+ or +nil+) of running the
- *  +block+ for every element in +enum+.
+ *  +block+ for every element in +lazy+.
  *
  *     (1..).lazy.filter_map { |i| i * 2 if i.even? }.take(5) #=> [4, 8, 12, 16, 20]
  *