Delete empty teardown

Author: raosush

test/rbs/rdoc/rbs_parser_test.rb

@@ -10,9 +10,6 @@ def parser(content)
     RBS::RDocPlugin::Parser.new(top_level, content)
   end
 
-  def teardown
-  end
-
   def test_class_decl_1
     parser = parser(<<~RBS)
 class A