Upgrade Outline to the latest release

[Pacerino]

Firstly, many thanks for the helmet chart! It has saved me a lot of work!

I would also like to point out that Outline now has a higher version than the one shown in this chart. I have adapted my Values.yaml to use the latest version.

Here are my changes i've made to use the latest version:

image:
  repository: outlinewiki/outline
  tag: 0.75.2

Because Outline wants to activate a Postgres plugin with the migration, Outline has to use the superuser as a workaround. So i've added this to the postgresql key.

postgresqlUsername: "postgres"

If this repo is still maintained, could you please update the helm chart? Thanks!