unicode_normalize/normalize.rb: simplify

* lib/unicode_normalize/normalize.rb (NF_HASH_{D,C,K}): remove
  first element by Hash#shift.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48045 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/unicode_normalize/normalize.rb

@@ -14,15 +14,15 @@ module UnicodeNormalize
   REGEXP_C = Regexp.compile(REGEXP_C_STRING, Regexp::EXTENDED)
   REGEXP_K = Regexp.compile(REGEXP_K_STRING, Regexp::EXTENDED)
   NF_HASH_D = Hash.new do |hash, key|
-                         hash.delete hash.first[0] if hash.length>MAX_HASH_LENGTH # prevent DoS attack
+                         hash.shift if hash.length>MAX_HASH_LENGTH # prevent DoS attack
                          hash[key] = nfd_one(key)
                        end
   NF_HASH_C = Hash.new do |hash, key|
-                         hash.delete hash.first[0] if hash.length>MAX_HASH_LENGTH # prevent DoS attack
+                         hash.shift if hash.length>MAX_HASH_LENGTH # prevent DoS attack
                          hash[key] = nfc_one(key)
                        end
   NF_HASH_K = Hash.new do |hash, key|
-                         hash.delete hash.first[0] if hash.length>MAX_HASH_LENGTH # prevent DoS attack
+                         hash.shift if hash.length>MAX_HASH_LENGTH # prevent DoS attack
                          hash[key] = nfkd_one(key)
                        end