fix: wearable portable experiences not treated as such in preview mode

[pravusjif]

this isPortableExperience value is being sent as FALSE for Wearable Portable Experiences in Preview Mode for their global scenes creation in the renderer.

The problem can be seen for example testing in preview mode this wearable portable experience: https://github.com/decentraland-scenes/calendar-px

For global portable experiences like this one that value seems to work fine.