The alias `openshell-prover` has been granted for OpenShell:
https://forum.snapcraft.io/t/alias-request-for-openshell/53658
Thus, we can remove guidance differentiating `openshell.prover` for the
snap from `openshell-prover` for other packaging formats. It is still
worth noting that installing a locally-built snap directly, rather than
from the store, means there is no alias.
Signed-off-by: Oliver Calder <oliver.calder@canonical.com>