Upgrade rubocop

test/integration/block_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class BlockTest < Minitest::Test
@@ -5,7 +7,7 @@ class BlockTest < Minitest::Test
 
   def test_unexpected_end_tag
     exc = assert_raises(SyntaxError) do
-      Template.parse("{% if true %}{% endunless %}")
+      Template.parse('{% if true %}{% endunless %}')
     end
     assert_equal exc.message, "Liquid syntax error: 'endunless' is not a valid delimiter for if tags. use endif"
   end