[DOC] Additional to Array#sample [ci skip]

* The requirement to the +n+ argument.
* The order of the result array.  [Misc #14147]

array.rb

@@ -49,6 +49,8 @@ class Array
   # But +self+ may contain duplicates:
   #    a = [1, 1, 1, 2, 2, 3]
   #    a.sample(a.size * 2) # => [1, 1, 3, 2, 1, 2]
+  # The argument +n+ must be a non-negative numeric value.
+  # The order of the result array is unrelated to the order of +self+.
   # Returns a new empty \Array if +self+ is empty.
   #
   # The optional +random+ argument will be used as the random number generator: