doc: improve cluster doc to highlith that provider_volume_type=STANDARD is not available for NVMW clusters (#1430)

Author: andreaangiolillo

website/docs/d/cluster.html.markdown

@@ -124,6 +124,7 @@ In addition to all arguments above, the following attributes are exported:
 * `provider_encrypt_ebs_volume` - **(DEPRECATED)** Indicates whether the Amazon EBS encryption is enabled. This feature encrypts the server’s root volume for both data at rest within the volume and data moving between the volume and the instance. By default this attribute is always enabled, per deprecation process showing the real value at `provider_encrypt_ebs_volume_flag` computed attribute. 
 * `provider_region_name` - Indicates 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/).
 * `provider_volume_type` - Indicates the type of the volume. The possible values are: `STANDARD` and `PROVISIONED`.
+-> **NOTE:** `STANDARD` is not available for NVME clusters.
 * `replication_factor` - (Deprecated) Number of replica set members. Each member keeps a copy of your databases, providing high availability and data redundancy. The possible values are 3, 5, or 7. The default value is 3.
 * `provider_auto_scaling_compute_min_instance_size` - Minimum instance size to which your cluster can automatically scale.
 * `provider_auto_scaling_compute_max_instance_size` - Maximum instance size to which your cluster can automatically scale.

website/docs/d/clusters.html.markdown

@@ -114,6 +114,7 @@ In addition to all arguments above, the following attributes are exported:
 * `provider_encrypt_ebs_volume` - **(DEPRECATED)** Indicates whether the Amazon EBS encryption is enabled. This feature encrypts the server’s root volume for both data at rest within the volume and data moving between the volume and the instance. By default this attribute is always enabled, per deprecation process showing the real value at `provider_encrypt_ebs_volume_flag` computed attribute. 
 * `provider_region_name` - Indicates 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/).
 * `provider_volume_type` - Indicates the type of the volume. The possible values are: `STANDARD` and `PROVISIONED`.
+-> **NOTE:** `STANDARD` is not available for NVME clusters.
 * `provider_auto_scaling_compute_min_instance_size` - Minimum instance size to which your cluster can automatically scale.
 * `provider_auto_scaling_compute_max_instance_size` - Maximum instance size to which your cluster can automatically scale.
 * `replication_factor` - (Deprecated) Number of replica set members. Each member keeps a copy of your databases, providing high availability and data redundancy. The possible values are 3, 5, or 7. The default value is 3.

website/docs/r/cluster.html.markdown

@@ -373,6 +373,8 @@ But in order to explicitly change `provider_instance_size_name` comment the `lif
 * `provider_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/).
     Do not specify this field when creating a multi-region cluster using the replicationSpec document or a Global Cluster with the replicationSpecs array.
 * `provider_volume_type` - (AWS - Optional) The type of the volume. The possible values are: `STANDARD` and `PROVISIONED`.  `PROVISIONED` is ONLY required if setting IOPS higher than the default instance IOPS.
+-> **NOTE:** `STANDARD` is not available for NVME clusters.
+
 * `replication_factor` - (Deprecated) Number of replica set members. Each member keeps a copy of your databases, providing high availability and data redundancy. The possible values are 3, 5, or 7. The default value is 3.
 * `provider_auto_scaling_compute_min_instance_size` - (Optional) Minimum instance size to which your cluster can automatically scale (e.g., M10). Required if `autoScaling.compute.scaleDownEnabled` is `true`.
 * `provider_auto_scaling_compute_max_instance_size` - (Optional) Maximum instance size to which your cluster can automatically scale (e.g., M40). Required if `autoScaling.compute.enabled` is `true`.