Clarify group owner removal [inability]

docs/resources/group.md

@@ -81,7 +81,7 @@ The following arguments are supported:
 * `mail_enabled` - (Optional) Whether the group is a mail enabled, with a shared group mailbox. At least one of `mail_enabled` or `security_enabled` must be specified. A group can be mail enabled _and_ security enabled.
 * `mail_nickname` - (Optional) The mail alias for the group, unique in the organisation. Required for mail-enabled groups. Changing this forces a new resource to be created.
 * `members` - (Optional) A set of members who should be present in this group. Supported object types are Users, Groups or Service Principals.
-* `owners` - (Optional) A set of object IDs of principals that will be granted ownership of the group. Supported object types are users or service principals. By default, the principal being used to execute Terraform is assigned as the sole owner. Groups cannot be created with no owners.
+* `owners` - (Optional) A set of object IDs of principals that will be granted ownership of the group. Supported object types are users or service principals. By default, the principal being used to execute Terraform is assigned as the sole owner. Groups cannot be created with no owners or have all their owners removed.
 
 -> **Group Ownership**  It's recommended to always specify one or more group owners, including the principal being used to execute Terraform, such as in the example above. When removing group owners, if a user principal has been assigned ownership, the last user cannot be removed as an owner. Microsoft 365 groups are required to always have at least one owner which _must be a user_ (i.e. not a service principal).