Since we have removed the last usage with
commit 12c6caa8
"Kill remaining PseudoSlots usage"

And remove corresponding support from the list-dispatch-commands script.

Also remove the now unused SFX_NEW_SLOT_ENUM macro

Change-Id: Id07c431de4404acf61a8bdd3507e390e5249879a
Reviewed-on: https://gerrit.libreoffice.org/35754Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>