Fix a typo [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63346 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_io.rb

@@ -633,7 +633,7 @@ class TestIO < Test::Unit::TestCase
           assert_equal(bigcontent[30, 40], File.read("bigdst"))
           assert_equal(0, f.pos)
         rescue NotImplementedError
-          #skip "pread(2) is not implemtented."
+          #skip "pread(2) is not implemented."
         end
       }
     }