pg_dump: Fix object-type sort priority for large objects.

pg_dump: Fix object-type sort priority for large objects.

Commit a45c78e328 moved large object metadata from SECTION_PRE_DATA
to SECTION_DATA but neglected to move PRIO_LARGE_OBJECT in
dbObjectTypePriorities accordingly.  While this hasn't produced any
known live bugs, it causes problems for a proposed patch that
optimizes upgrades with many large objects.  Fixing the priority
might also make the topological sort step marginally faster by
reducing the number of ordering violations that have to be fixed.

Reviewed-by: Nitin Motiani <nitinmotiani@google.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/aBkQLSkx1zUJ-LwJ%40nathan
Discussion: https://postgr.es/m/aG_5DBCjdDX6KAoD%40nathan
Backpatch-through: 17