pgsql: CREATE STATISTICS: improve misleading error message

CREATE STATISTICS: improve misleading error message

The previous change (commit f225473cbae) was still not on target,
because it talked about relation kinds, which are not what is being
checked here. Provide a more accurate message.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: /messages/by-id/CACJufxEZ48toGH0Em_6vdsT57Y3L8pLF=DZCQ_gCii6=C3MeXw@mail.gmail.com

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/4529861cc40886ec57de185fa0fa55f2a0c08c25

Modified Files
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src/backend/tcop/utility.c | 3 +--
src/test/regress/expected/stats_ext.out | 18 ++++++------------
2 files changed, 7 insertions(+), 14 deletions(-)