pgsql: doc: Formatting improvements

doc: Formatting improvements

Small touch-up on commits 25505082f0e and 50fd428b2b9. Fix the
formatting of the example messages in the documentation and adjust the
wording to match the code.

Branch
------
REL_18_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/f15c00e90930e58730a930f2a8ed1e2df34222a0

Modified Files
--------------
doc/src/sgml/logicaldecoding.sgml | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)