deps: bump datadog-api-client to v2.31.0

[inikotoran]

Bumping datadog-api-client to latest available version (v2.31.0)

In particular, with the latest version I'd like to enable import for datadog_service_level_objective resource with type = time_slice

I've tested this locally to import time_slice SLO

➜  go run main.go import datadog --resources=service_level_objective --filter="service_level_objective=id:$SLO_ID" --api-key "$DD_API_KEY" --app-key "$DD_APP_KEY"

Result:

resource "datadog_service_level_objective" "tfer--service_level_objective_id" {
  name = "test time_slice"

  sli_specification {
    time_slice {
      comparator = ">"

      query {
        formula {
          formula_expression = "default_zero(query1)"
        }

        query {
          metric_query {
            data_source = "metrics"
            name        = "query1"
            query       = "sum:http.client.hits{}.as_count()"
          }
        }
      }

      query_interval_seconds = "300"
      threshold              = "0"
    }
  }

  tags             = []
  target_threshold = "99.9"

  thresholds {
    target    = "99.9"
    timeframe = "7d"
    warning   = "0"
  }

  timeframe = "7d"
  type      = "time_slice"
}

[inikotoran]

hi @sergeylanzman,
Can you help to review this PR? or redirect me to the information on how to get it reviewed?
I can't find anything in the CONTRIBUTING file
Thanks!
*sorry for tagging you (I saw your name in the AUTHOR file)