[TFDN-1107] update docs for atlas agent sort (#777)

Adding documentation for a new sort by created-at feature in the agents
list endpoint added here: hashicorp/atlas#24262

Author: twitnithegirl

content/terraform-docs-common/docs/cloud-docs/api-docs/agents.mdx

@@ -190,11 +190,12 @@ curl \
 
 This endpoint supports pagination [with standard URL query parameters](/terraform/cloud-docs/api-docs#query-parameters). Remember to percent-encode `[` as `%5B` and `]` as `%5D` if your tooling doesn't automatically encode URLs.
 
-| Parameter                 | Description                                                                  |
-| ------------------------- | ---------------------------------------------------------------------------- |
-| `filter[last-ping-since]` | **Optional.** Accepts a date in ISO8601 format (ex. `2020-08-11T10:41:23Z`). |
-| `page[number]`            | **Optional.** If omitted, the endpoint will return the first page.           |
-| `page[size]`              | **Optional.** If omitted, the endpoint will return 20 agents per page.       |
+| Parameter                 | Description                                                                                                                                                         |
+| ------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `filter[last-ping-since]` | **Optional.** Accepts a date in ISO8601 format (ex. `2020-08-11T10:41:23Z`).                                                                                        |
+| `page[number]`            | **Optional.** If omitted, the endpoint will return the first page.                                                                                                  |
+| `page[size]`              | **Optional.** If omitted, the endpoint will return 20 agents per page.                                                                                              |
+| `sort`                    | **Optional.** Allows sorting the returned agents. Valid value is `"created-at"`. Prepending a hyphen to the sort parameter will reverse the order (e.g. `"-created-at"`). |
 
 ### Sample Request