docs(AWS/S3):Mention 'api-endpoint' & 'api-region' are optional (#1736)

* Mention 'api-endpoint' & 'api-region' are optional

Explained the need for 'api-endpoint' & 'api-region' flags are optional and only if using Minio
to avoid confusions for beginners.

* Address PR review comments

* Move out Note to a separate section

Co-authored-by: brian-armory <53799971+brian-armory@users.noreply.github.com>

setup/artifacts/s3.md

@@ -37,6 +37,8 @@ ARTIFACT_ACCOUNT_NAME=my-s3-account
        --region $REGION
    ```
 
+**Note:** Setting `--api-endpoint` & `--api-region` is optional. It is needed only if you are using a S3 clone such as Minio. 
+
 There are more options described
 [here](/reference/halyard/commands#hal-config-artifact-s3-account-edit)
 if you need more control over your configuration.