ignore jasmine gem's browser configuration for using rake task's configuration

sauce gem's browser configuration is overridden by jasmine gem's configuration.
https://github.com/pivotal/jasmine-gem/blob/v1.3.2/lib/jasmine/run_specs.rb#L20
https://github.com/sauce-labs/sauce_ruby/blob/v2.4.1/lib/sauce/config.rb#L63
Consequently each rake task's configuration is ignored.