Use in_progress workflow_job example, not queued (#22880)

* Use in_progress workflow_job example, not queued

### tl;dr

This changes the example `workflow_job` payload to be an `in_progress` event instead of `queued` event.

### why

In #22174, I added some keys to the example workflow_job json. This was correct, but by adding non-null _values_, **I introduced a subtle bug**.

It's a bug because a `queued` workflow is—by definition—_not_ yet assigned to a runner. So all the `runner_*` attributes will be `null` in the real world. 

After the workflow becomes `in_progress`, all the values are guaranteed to exist. So let's change the example to be an `in_progress` event, since it's a better example for documentation.

* Explain more about the runner_* attributes in "workflow_job_properties.md"

* Consistentize naming

Co-authored-by: Martin Lopes <martin389@github.com>
Co-authored-by: hubwriter <hubwriter@github.com>

Author: 3 people

data/reusables/webhooks/workflow_job_properties.md

@@ -2,3 +2,9 @@ Key | Type | Description
 ----|------|-------------
 `action`|`string` | The action performed. Can be one of: <ul><li> `queued` - A new job was created.</li><li> `in_progress` - The job has started processing on the runner.</li><li> `completed` - The `status` of the job is `completed`.</li></ul>
 `workflow_job`|`object`| The workflow job. Many `workflow_job` keys, such as `head_sha`, `conclusion`, and `started_at` are the same as those in a [`check_run`](#check_run) object.
+`workflow_job[status]`|`string`| The current status of the job. Can be `queued`, `in_progress`, or `completed`.
+`workflow_job[labels]`|`array`| Custom labels for the job. Specified by the [`"runs-on"` attribute](/actions/reference/workflow-syntax-for-github-actions#jobsjob_idruns-on) in the workflow YAML.
+`workflow_job[runner_id]`|`integer`| The ID of the runner that is running this job. This will be `null` as long as `workflow_job[status]` is `queued`.
+`workflow_job[runner_name]`|`string`| The name of the runner that is running this job. This will be `null` as long as `workflow_job[status]` is `queued`.
+`workflow_job[runner_group_id]`|`integer`| The ID of the runner group that is running this job. This will be `null` as long as `workflow_job[status]` is `queued`.
+`workflow_job[runner_group_name]`|`string`| The name of the runner group that is running this job. This will be `null` as long as `workflow_job[status]` is `queued`.

lib/webhooks/static/dotcom/workflow_job.payload.json

@@ -1,5 +1,5 @@
 {
-  "action": "queued",
+  "action": "in_progress",
   "workflow_job": {
     "id": 2832853555,
     "run_id": 940463255,
@@ -8,13 +8,20 @@
     "head_sha": "e3103f8eb03e1ad7f2331c5446b23c070fc54055",
     "url": "https://api.github.com/repos/octo-org/example-workflow/actions/jobs/2832853555",
     "html_url": "https://github.com/octo-org/example-workflow/runs/2832853555",
-    "status": "queued",
+    "status": "in_progress",
     "conclusion": null,
     "started_at": "2021-06-15T19:22:27Z",
     "completed_at": null,
     "name": "Test workflow",
     "steps": [
-
+      {
+        "name": "Set up job",
+        "status": "in_progress",
+        "conclusion": null,
+        "number": 1,
+        "started_at": "2021-06-15T19:22:27.000Z",
+        "completed_at": null
+      }
     ],
     "check_run_url": "https://api.github.com/repos/octo-org/example-workflow/check-runs/2832853555",
     "labels": [