POSTGRES_PASSWORD vs POSTGRES_PASSWORD_FILE

I believe that there is an issue with the following documentation:

- https://docs.goauthentik.io/install-config/install/kubernetes/#set-values

In this example the PostgreSQL password will be set as environment variable `POSTGRES_PASSWORD`, but the Helm chart for PostgreSQL has set the value `auth.usePasswordFiles` to `true`, which will add an additional environment variable `POSTGRES_PASSWORD_FILE`.

- https://github.com/goauthentik/helm/blob/main/charts/authentik/Chart.yaml#L31-L35
- https://github.com/bitnami/charts/blob/main/bitnami/postgresql/values.yaml#L179-L181

In this case the start of `pod/authentik-postgresql-0` will end up in the status `CrashLoopBackOff`, because both environment variables are mutually exclusive.

Instead the documentation should add the following parameter:

```
postgresql:
enabled: true
auth:
password: "ThisIsNotASecurePassword"
usePasswordFiles: false
```