Deprecate DAST domain validation variable

The work for deprecation is being completed in 13.11, but the feature
was deprecated in 13.8. See
https://gitlab.com/gitlab-com/www-gitlab-com/-/merge_requests/71418 for
the deprecation release post.

doc/user/application_security/dast/index.md

@@ -653,7 +653,7 @@ DAST can be [configured](#customizing-the-dast-settings) using CI/CD variables.
 | `DAST_MASK_HTTP_HEADERS`     | string  | Comma-separated list of request and response headers to be masked (GitLab 13.1). Must contain **all** headers to be masked. Refer to [list of headers that are masked by default](#hide-sensitive-information). |
 | `DAST_EXCLUDE_URLS`          | URLs    | The URLs to skip during the authenticated scan; comma-separated. Regular expression syntax can be used to match multiple URLs. For example, `.*` matches an arbitrary character sequence. Not supported for API scans. |
 | `DAST_FULL_SCAN_ENABLED`     | boolean | Set to `true` to run a [ZAP Full Scan](https://github.com/zaproxy/zaproxy/wiki/ZAP-Full-Scan) instead of a [ZAP Baseline Scan](https://github.com/zaproxy/zaproxy/wiki/ZAP-Baseline-Scan). Default: `false` |
-| `DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED` | boolean | Set to `true` to require [domain validation](#domain-validation) when running DAST full scans. Not supported for API scans. Default: `false` |
+| `DAST_FULL_SCAN_DOMAIN_VALIDATION_REQUIRED` | boolean | [Deprecated](https://gitlab.com/gitlab-org/gitlab/-/issues/293595) in GitLab 13.8, to be removed in 14.0. Set to `true` to require [domain validation](#domain-validation) when running DAST full scans. Not supported for API scans. Default: `false` |
 | `DAST_AUTO_UPDATE_ADDONS`    | boolean | ZAP add-ons are pinned to specific versions in the DAST Docker image. Set to `true` to download the latest versions when the scan starts. Default: `false` |
 | `DAST_API_HOST_OVERRIDE`     | string  | Used to override domains defined in API specification files. Only supported when importing the API specification from a URL. Example: `example.com:8080` |
 | `DAST_EXCLUDE_RULES`         | string  | Set to a comma-separated list of Vulnerability Rule IDs to exclude them from running during the scan. Rule IDs are numbers and can be found from the DAST log or on the [ZAP project](https://github.com/zaproxy/zaproxy/blob/develop/docs/scanners.md). For example, `HTTP Parameter Override` has a rule ID of `10026`. **Note:** In earlier versions of GitLab the excluded rules were executed but alerts they generated were suppressed. [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/118641) in GitLab 12.10. |