pgsql: Unify gratuitously different error messages

Unify gratuitously different error messages

Fixup for commit 37188cea0c.

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/3a788447d85e2643f70a8d50f16a526328bfc092

Modified Files
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src/bin/pg_dump/pg_dump.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)