[VM] Clarify that encrypt-format-all is only applicable to Linux VMs (#21743)

Author: nachoalonsoportillo

src/azure-cli/azure/cli/command_modules/vm/_params.py

@@ -472,7 +472,7 @@ def load_arguments(self, _):
         c.argument('disk_name', arg_type=name_arg_type, help='The data disk name.')
 
     with self.argument_context('vm encryption enable') as c:
-        c.argument('encrypt_format_all', action='store_true', help='Encrypts-formats data disks instead of encrypting them. Encrypt-formatting is a lot faster than in-place encryption but wipes out the partition getting encrypt-formatted.')
+        c.argument('encrypt_format_all', action='store_true', help='Encrypts-formats data disks instead of encrypting them. Encrypt-formatting is a lot faster than in-place encryption but wipes out the partition getting encrypt-formatted. (Only supported for Linux virtual machines.)')
         # Place aad arguments in their own group
         aad_arguments = 'Azure Active Directory'
         c.argument('aad_client_id', arg_group=aad_arguments)