Note use of direct conneciton with --split-cluser

I found that when using `--split-cluster` you should also use direct connections, otherwise it just only connects to the same replica and reports its metrics as if all the replicas have exactly the same metric values.

Author: dobesv

REFERENCE.md

@@ -8,10 +8,10 @@
 | --[no-]discovering-mode           | Enable autodiscover collections                                                                                                                                               |                                                                  |
 | --mongodb.collstats-colls         | List of comma separared databases.collections to get $collStats                                                                                                               | --mongodb.collstats-colls=db1,db2.col2                           |
 | --mongodb.indexstats-colls        | List of comma separared databases.collections to get $indexStats                                                                                                              | --mongodb.indexstats-colls=db1.col1,db2.col2                     |
-| --[no-]mongodb.direct-connect     | Whether or not a direct connect should be made. Direct connections are not valid if multiple hosts are specified or an SRV URI is used                                        |                                                                  |
+| --[no-]mongodb.direct-connect     | Whether or not a direct connect should be made. Direct connections are not valid if multiple hosts are specified or an SRV URI is used unless using --split-cluster           |                                                                  |
 | --[no-]mongodb.global-conn-pool   | Use global connection pool instead of creating new pool for each http request                                                                                                 |                                                                  |
 | --mongodb.uri                     | MongoDB connection URI ($MONGODB_URI)                                                                                                                                         | --mongodb.uri=mongodb://user:pass@127.0.0.1:27017/admin?ssl=true |
-| --split-cluster                   | Whether to treat cluster members from the connection URI as separate targets                                                                                                  |
+| --split-cluster                   | Whether to treat cluster members from the connection URI as separate targets, use with `--mongodb.direct-connect` and the `/scrapeall` endpoint                               |                                                                  |
 | --web.listen-address              | Address to listen on for web interface and telemetry                                                                                                                          | --web.listen-address=":9216"                                     |
 | --web.telemetry-path              | Metrics expose path                                                                                                                                                           | --web.telemetry-path="/metrics"                                  |
 | --web.config                      | Path to the file having Prometheus TLS config for basic auth                                                                                                                  | --web.config=STRING                                              |