Fix test using Ruby 2.7 positional arguments

This was originally fixed in 12537f6
but was accidentally undone in d28a941.

Author: peterzhu2118

test/unit/block_test.rb

@@ -115,11 +115,11 @@ def read_template_file(template_path)
   def test_include_partial_with_syntax_error
     old_file_system = Liquid::Template.file_system
     begin
-      Liquid::Template.file_system = StubFileSystem.new(
+      Liquid::Template.file_system = StubFileSystem.new({
         "invalid" => "{% foo %}",
         "valid" => '{% include "nested" %}',
         "nested" => "valid",
-      )
+      })
 
       template = Liquid::Template.parse("{% include 'invalid' %},{% include 'valid' %}")
       assert_equal("Liquid syntax error: Unknown tag 'foo',valid", template.render)