Base postgres image changed, update docs to reflect

doc/ci/services/postgres.md

@@ -22,12 +22,13 @@ services:
 variables:
   POSTGRES_DB: nice_marmot
   POSTGRES_USER: runner
-  POSTGRES_PASSWORD: "runner-password"
+  POSTGRES_PASSWORD: ""
+  POSTGRES_HOST_AUTH_METHOD: trust
 ```
 
 NOTE: **Note:**
-The `POSTGRES_DB`, `POSTGRES_USER`, and `POSTGRES_PASSWORD` variables can't be set in
-the GitLab UI. To set them, assign them to a variable
+The `POSTGRES_DB`, `POSTGRES_USER`, `POSTGRES_PASSWORD` and `POSTGRES_HOST_AUTH_METHOD`
+variables can't be set in the GitLab UI. To set them, assign them to a variable
 [in the UI](../variables/README.md#via-the-ui), and then assign that
 variable to the `POSTGRES_DB`, `POSTGRES_USER`, and `POSTGRES_PASSWORD` variables in
 your `.gitlab-ci.yml`.