Thread: pgsql: doc: Fix up title case

doc: Fix up title case

This fixes some instances that were missed in earlier processings and
that now look a bit strange because they are inconsistent with nearby
titles.

Branch
------
REL_13_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/62340f8eca4c9d4e49097eaf0a341aca8450b56b

Modified Files
--------------
doc/src/sgml/dml.sgml     | 2 +-
doc/src/sgml/func.sgml    | 2 +-
doc/src/sgml/plpgsql.sgml | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)