pgsql: doc: clarify text about combining row-level policies

doc: clarify text about combining row-level policies

Reported-by: splarv@ya.ru

Discussion: /messages/by-id/173045909386.700.9231055113418242392@wrigleys.postgresql.org

Backpatch-through: master

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/cffca3665d8238dddf7afb4a3404866e375195c5

Modified Files
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doc/src/sgml/ddl.sgml | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)