test_module.rb: rename

* test/ruby/test_module.rb (test_visibility_by_public_class_method):
  rename because anonymousness is not a point.
  [ruby-core:54404] [Bug #8284]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40371 b2dd03c8-39d4-4d8f-98ff-823fe69b080e