(DOCSP-30111): Added official image advantages. (#1301)

* (DOCSP-30111): Added official image advantages.

* (DOCSP-30111): Incorporated Sebastian's and Nam's feedback.

Author: corryroot

docs/install-upgrade.md

@@ -170,6 +170,14 @@ for MongoDB Docker images:
 
 1. In the Operator [resource definition](../config/manager/manager.yaml), set the `MONGODB_IMAGE` and `MONGODB_REPO_URL` environment variables:
 
+   **NOTE:** Use the official 
+   [MongoDB Community Server images](https://hub.docker.com/r/mongodb/mongodb-community-server). 
+   Official images provide the following advantages:
+
+   - They are rebuilt daily for the latest upstream 
+     vulnerability fixes.
+   - MongoDB tests, maintains, and supports them.
+
    | Environment Variable | Description | Default                      |
    |----|------------------------------|----|
    | `MONGODB_IMAGE` | From the `MONGODB_REPO_URL`, absolute path to the MongoDB Docker image that you want to deploy. | `"mongodb-community-server"` |