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_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/40316dfedc10155f90eb71314b57a86f6e11bd0e

Modified Files
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src/backend/access/brin/brin_revmap.c | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)