Drop the Depends on tablet-browser-ui for Diablo, for now

Drop the Depends on tablet-browser-ui for Diablo, for now

tablet-browser-ui is in the Diablo rootfs image, which means that (1)
everyone has it and (2) the maemo.org packages interface doesn't know
that it exists.  Since the packages interface bug now prevents new
versions of browser-switchboard for Diablo from going to extras, work
around this for now by losing the dependency.

See https://bugs.maemo.org/show_bug.cgi?id=8806 for more information.