pgsql: doc: Clarify requirements for SET ROLE.

doc: Clarify requirements for SET ROLE.

Since commit 3d14e171e9, SET ROLE has required the current session
user to have membership with the SET option in the target role, but
the SET ROLE documentation only mentions the membership
requirement.  This commit adds this important detail to the SET
ROLE page.

Reviewed-by: Robert Haas
Discussion: https://postgr.es/m/CA%2BRLCQysHtME0znk2KUMJN343ksboSRQSU-hCnOjesX6VK300Q%40mail.gmail.com
Backpatch-through: 16

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3330a8d1b792375ae3f7dffb7eb0a45c907cbc72

Modified Files
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doc/src/sgml/ref/set_role.sgml | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)