Package is deprecated

[slyon]

As per upstream Kartik Nema (@kartnema) the pkg-urm-ext package is going away (to be merged into pkg-urm):

We are currently making some recently planned structural changes to our projects for easier maintenance. We are merging URM-Extensions (which mostly contains target specific configs and plugins) into the main project URM itself, i.e. we are planning to keep only one project. Post this merge completion, there will be only a single Debian build / packaging repo: pkg-urm