pgsql: docs: clarify new aggressive vacuum mode for multi-xacts

docs: clarify new aggressive vacuum mode for multi-xacts

Reported-by: eric.mutta@gmail.com

Discussion: /messages/by-id/162395467510.686.11947486273299446208@wrigleys.postgresql.org

Backpatch-through: 14

Branch
------
REL_14_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/d54092955690e29656186ff5d4d315a3c56ccb37

Modified Files
--------------
doc/src/sgml/maintenance.sgml | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)