Fixes tests for latest Rails 6.1

[zedtux]

The test suite is broken with the latest Rails 6.1 series:

==> Devise.orm = :active_record
/usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support/logger_thread_safe_level.rb:16:in `<module:LoggerThreadSafeLevel>': uninitialized constant ActiveSupport::LoggerThreadSafeLevel::Logger (NameError)

    Logger::Severity.constants.each do |severity|
    ^^^^^^
	from /usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support/logger_thread_safe_level.rb:9:in `<module:ActiveSupport>'
	from /usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support/logger_thread_safe_level.rb:8:in `<top (required)>'
	from /usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support/logger_silence.rb:5:in `require'
	from /usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support/logger_silence.rb:5:in `<top (required)>'
	from /usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support/logger.rb:3:in `require'
	from /usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support/logger.rb:3:in `<top (required)>'
	from /usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support.rb:29:in `require'
	from /usr/local/bundle/gems/activesupport-6.1.7.10/lib/active_support.rb:29:in `<top (required)>'
	from /usr/local/bundle/gems/railties-6.1.7.10/lib/rails.rb:7:in `require'
	from /usr/local/bundle/gems/railties-6.1.7.10/lib/rails.rb:7:in `<top (required)>'
	from /usr/local/bundle/gems/actionpack-6.1.7.10/lib/action_controller/railtie.rb:3:in `require'
	from /usr/local/bundle/gems/actionpack-6.1.7.10/lib/action_controller/railtie.rb:3:in `<top (required)>'
        ...

This PR fixes it.