adds M0 (#2730)

Author: lantoli

docs/resources/advanced_cluster.md

@@ -558,7 +558,7 @@ If you are upgrading a replica set to a sharded cluster, you cannot increase the
   - `AWS` - Amazon AWS
   - `GCP` - Google Cloud Platform
   - `AZURE` - Microsoft Azure
-  - `TENANT` - M2 or M5 multi-tenant cluster. Use `replication_specs.#.region_configs.#.backing_provider_name` to set the cloud service provider.
+  - `TENANT` - M0, M2 or M5 multi-tenant cluster. Use `replication_specs.#.region_configs.#.backing_provider_name` to set the cloud service provider.
 * `read_only_specs` - (Optional) Hardware specifications for read-only nodes in the region. Read-only nodes can become the [primary](https://docs.atlas.mongodb.com/reference/glossary/#std-term-primary) and can enable local reads. If you don't specify this parameter, no read-only nodes are deployed to the region. See [below](#specs)
 * `region_name` - (Optional) Physical location of your MongoDB cluster. The region you choose can affect network latency for clients accessing your databases.  Requires the **Atlas region name**, see the reference list for [AWS](https://docs.atlas.mongodb.com/reference/amazon-aws/), [GCP](https://docs.atlas.mongodb.com/reference/google-gcp/), [Azure](https://docs.atlas.mongodb.com/reference/microsoft-azure/).