fix typo.

test/t/enumerable.rb

@@ -106,7 +106,7 @@ assert('Enumerable#member?', '15.3.2.2.15') do
   assert_false [1,2,3,4,5,6,7,8,9].member?(0)
 end
 
-assert('Enumerable#partion', '15.3.2.2.16') do
+assert('Enumerable#partition', '15.3.2.2.16') do
   [0,1,2,3,4,5,6,7,8,9].partition do |i|
     i % 2 == 0
   end == [[0,2,4,6,8], [1,3,5,7,9]]