Specify hosts in bug report template.

Host authentication introduced by #33145 allows only "0.0.0.0/0", "::/0"
and "localhost" in the development environment.
4298df00ae/railties/lib/rails/application/configuration.rb (L33)

But `rack-test` use `example.org` for default host.
6c07bf53ad/lib/rack/test.rb (L13)

Therefore, if `hosts` is not specified, host authentication rejects
the request.

In Travis CI, this problem does not occur because `test` is specified
by default in `RAILS_ENV` and `RACK_ENV`.
https://docs.travis-ci.com/user/environment-variables/#default-environment-variables

If user actually use it, env may not always be specified. Explicitly
specify hosts in the file so that it works in any environment.

guides/bug_report_templates/action_controller_master.rb

@@ -14,6 +14,7 @@ require "action_controller/railtie"
 
 class TestApp < Rails::Application
   config.root = __dir__
+  config.hosts << "example.org"
   secrets.secret_key_base = "secret_key_base"
 
   config.logger = Logger.new($stdout)