fix marginalia for postgres update/delete statements

temporarily uses our own gem again, until this gets merged upstream.

test plan: enable it in marginalia.yml , then verify that updates and
deletes get logged with the expected comment. i used the console:

Setting.create!(name: 'x', value: 'x').tap { |s| s.touch }.destroy

Change-Id: I5319551ffc4ac1444de3c78d094342cc79c6340c
Reviewed-on: https://gerrit.instructure.com/39982
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>