normalize.rb: fix syntax error

* lib/unicode_normalize/normalize.rb (normalized): fix syntax
  error, `when` clase allows `*` but not `**`.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48340 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/unicode_normalize/normalize.rb

@@ -158,7 +158,7 @@ module UnicodeNormalize
       end
     when Encoding::US_ASCII
       true
-    when **UNICODE_ENCODINGS
+    when *UNICODE_ENCODINGS
       normalized? string.encode(Encoding::UTF_8), form
     else
       raise Encoding::CompatibilityError, "Unicode Normalization not appropriate for #{encoding}"