pgsql: doc: clarify recursion internal behavior

doc: clarify recursion internal behavior

Reported-by: Drew DeVault

Discussion: /messages/by-id/20211018091720.31299-1-sir@cmpwn.com

Backpatch-through: 10

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/170704da68c5150776c0ee4ed51350acde47b4a5

Modified Files
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doc/src/sgml/queries.sgml | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)