pgsql: Remove WARNING message from brin_desummarize_range

Remove WARNING message from brin_desummarize_range

This message was being emitted on the grounds that only crashed
summarization could cause it, but in reality even an aborted vacuum
could do it ... which makes it way too noisy, particularly since it
shows up in regression tests and makes them die.

Reported by Tom Lane.
Discussion: https://postgr.es/m/489091.1593534251@sss.pgh.pa.us

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/c3a79e71929a6b5cdd2416ab4976dab59736c937

Modified Files
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src/backend/access/brin/brin_revmap.c | 24 ++++++++----------------
1 file changed, 8 insertions(+), 16 deletions(-)