Simplifying test and fixing formatting issue

Author: aguspe

rb/spec/unit/selenium/webdriver/firefox/service_spec.rb

@@ -81,7 +81,7 @@ module Firefox
             service = described_class.new
             ws_index = service.extra_args.index('--websocket-port')
             port = service.extra_args[ws_index + 1].to_i
-            expect(port).to be.positive?
+            expect(port).to be_positive
           end
 
           context 'with connect existing' do