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
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/7f055fba3fa99d807837a229967fd6c5dd720530
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(-)
