Chnaged machine_name to machine_account

[bjerrecs]

This change updates the docs to match what's required by the provider

Before

machine_accounts = [
      {
          machines = [
              {
                  machine_name= "Domain\\MachineName"
              },
              {
                  machine_name= "Domain\\MachineName"
              }
          ]
      }
]

After

machine_accounts = [
      {
          machines = [
              {
                  machine_account = "Domain\\MachineName"
              },
              {
                  machine_account = "Domain\\MachineName"
              }
          ]
      }
]

[AlanCitrix]

Thank you for the PR, we will have this fixed in the next release!

[aneeshk-citrix]

This is now fixed in the release v0.6.1. Closing PR