pgsql: psql: Improve descriptions of \\flush[request] in --help

psql: Improve descriptions of \\flush[request] in --help

Noah has reported that the current wording was confusing compared to the
description of the underlying libpq routine.  The new wording is from
me.

Reported-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/20250415213450.1f.nmisch@google.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5743d122fcf35edba801609fcde7410610ed0f19

Modified Files
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src/bin/psql/help.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)