Fix bogus commutator/negator links for JSONB containment operators.

<@ and @> are each other's commutators, but they were incorrectly marked
as being each other's negators instead.  (This was actually questioned
in a comment in the original commit, but nobody followed through :-(.)
Per bug #11178 from Christian Pronovost.

In passing, fix some JSONB operator descriptions that were randomly
different from the phrasing of every other similar description.

catversion bump for pg_catalog contents change.