pgsql: doc: mention the pg_locks lock names in parentheses

doc: mention the pg_locks lock names in parentheses

Reported-by: Troy Frericks

Discussion: /messages/by-id/165653551130.665.8240515669521441325@wrigleys.postgresql.org

Backpatch-through: 10

Branch
------
REL_10_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/88580b63ebe4597b6b3ef6ad23c7370af2e9cadc

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