Bug Fix Enumerator::Lazy#uniq state for multiple call

	* enumerator.c (lazy_uniq_i): create new hash for each calls.
	  [Fix GH-1820]

	Currently

		2.5.0-preview1 :001 > arr = (0..100).lazy.uniq{|i| i % 10}
		 => #<Enumerator::Lazy: #<Enumerator::Lazy: 0..100>:uniq>
		2.5.0-preview1 :002 > arr.to_a
		 => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
		2.5.0-preview1 :003 > arr.to_a
		 => []

	Expected

	arr.to_a to always return same output

	From: Anmol Chopra <anmolchopra@rocketbox.in>

	test_enumerator.rb: duplicate assertions

	* test/ruby/test_enumerator.rb (test_uniq): remove assertions
	  which ared duplicate of lazy enumerator tests in
	  test_lazy_enumerator.rb.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@63824 b2dd03c8-39d4-4d8f-98ff-823fe69b080e