fix: Support WAITING status for [GitHubDeployments]

[martincostello]

Fix "invalid response data" badge label for GitHub deployments pending approval.

Scenario

If a deployment is pending manual approval:

Then the GraphQL API reports the status as PENDING:

Request

query {
  repository(owner: "martincostello", name: "api") {
    deployments(last: 1, environments: ["production"]) {
      nodes {
        latestStatus {
          state
        }
      }
    }
  }
}

Response

{
  "data": {
    "repository": {
      "deployments": {
        "nodes": [
          {
            "latestStatus": {
              "state": "WAITING"
            }
          }
        ]
      }
    }
  }
}

This then produces a badge that looks like this:

The status doesn't appear to be consistently documented, but definitely exists: octokit/webhooks.net#52

[shields-ci]

	Warnings
⚠️	This PR modified service code for github but not its test code. That's okay so long as it's refactoring existing code.

	Messages
📖	✨ Thanks for your contribution to Shields, @martincostello!

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