Fix typo [ci skip]

Author: nobu

test/optparse/test_did_you_mean.rb

@@ -44,7 +44,7 @@ def test_verbose
     end
   end
 
-  def test_ambiguos
+  def test_ambiguous
     assert_raise_with_message(OptionParser::AmbiguousOption, /ambiguous option: --ba\nDid you mean\?\s+bar\s+baz\Z/) do
       @opt.permute!(%w"--ba")
     end