caos.backends.pgsql.delta: Make sure table inheritance gets established once
caos.backends.pgsql.delta: Make sure table inheritance gets established once

In theory rebase should not contain bases that are already present in
the parent set, but this can happen for virtual concept due to
incomplete introspection.  Just add negative TableInherits condition for
now.

edgedb/edgedb,edgedb/edgedb,edgedb/edgedb