Un-break pg_dump for pre-8.3 source servers.

Un-break pg_dump for pre-8.3 source servers.

Commit 07b39083c inserted an unconditional reference to pg_opfamily,
which of course fails on servers predating that catalog.  Fortunately,
the case it's trying to solve can't occur on such old servers (AFAIK).
Hence, just skip the additional code when the source predates 8.3.

Per bug #15955 from sly.  Back-patch to all supported branches,
like the previous patch.

Discussion: https://postgr.es/m/15955-1daa2e676e903d87@postgresql.org