pgsql: docs: Add command tags for SQL commands

docs: Add command tags for SQL commands

Commit 6c3ffd6 added a couple new predefined roles but didn't properly
wrap the SQL commands mentioned in the description of those roles with
command tags, so add them now.

Backpatch-through: 14
Reported-by: Michael Banck
Discussion: https://postgr.es/m/606d8b1c.1c69fb81.3df04.1a99@mx.google.com

Branch
------
REL_14_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/8f6c110349769e2b6375cd01e632199a104dc4a1

Modified Files
--------------
doc/src/sgml/user-manag.sgml | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)