Reconsider update instructions for product

In our update instructions, we list the possibility of an 'in-place update' of the product. This won't work. We don't have any update sites in the product besides a specific version of Eclipse and a specific version of Orbit. Thus, new versions of Eclipse and Orbit won't be found. Also, we don't have any Eclipse ESCET update sites added, so no new versions of that will be found either. Furthermore, we have update sites per specific version, and no composite one that includes all of them. As such, there is currently no update site URL that we could even configure in the product that will allow updating to a later version. For now, I propose to remove the in-place update instructions, and only allow downloading a new release, the 'side-by-side update' variant.