enable ionic@6 travis test build
enable ionic@6 travis test build

hit0907/cordova-plugin-iosrtc,BasqueVoIPMafia/cordova-plugin-iosrtc,hit0907/cordova-plugin-iosrtc,hit0907/cordova-plugin-iosrtc,BasqueVoIPMafia/cordova-plugin-iosrtc,BasqueVoIPMafia/cordova-plugin-iosrtc,eface2face/cordova-plugin-iosrtc,eface2face/cordova-plugin-iosrtc,eface2face/cordova-plugin-iosrtc