[fix] Change client validation of permissions revoke type

[albertchang]

Description

Currently, we'll get an error if we try to revoke >1 permission of mixed types, like this:

resource "retool_permissions" "test_permissions" {
  subject = {
    type = "group"
    id   = retool_group.test_group.id
  }
  permissions = [
    {
      object = {
        type = "folder"
        id   = retool_folder.test_folder2.id
      }
      access_level = "use"
    },
    {
      object = {
        type = "folder"
        id   = retool_folder.test_folder3.id
      }
      access_level = "own"
    },
  ]
}

This is because the client sdk throws an error when the response type of the permissions endpoint contains more than one "object" type, as visible here in the spec:

This is an imprecise mapping of our internal discriminated unions to the openapi spec, since in reality it's possible for our permission group to have multiple types of objects. To resolve, I manually updated the definition in our spec and regenerated the client code to accept anyOf.

Tests

Manually tried to apply and destroy the above terraform, and confirmed there are no errors.

[albertchang]

Not sure why this started breaking, but we get a complaint about missing terraform binary, so I added a step to install it.