Add analyzer setting entry for `SAST_SEMGREP_METRICS`

doc/user/application_security/sast/index.md

@@ -493,7 +493,8 @@ Some analyzers can be customized with CI/CD variables.
 | `FAIL_NEVER`                | SpotBugs   | Set to `1` to ignore compilation failure.                                                                                                                                                                                          |
 | `SAST_GOSEC_CONFIG`         | Gosec      | Path to configuration for Gosec (optional).                                                                                                                                                                                        |
 | `PHPCS_SECURITY_AUDIT_PHP_EXTENSIONS` | phpcs-security-audit | Comma separated list of additional PHP Extensions.                                                                                                                                                             |
-| `SAST_DISABLE_BABEL`        | NodeJsScan | Disable Babel processing for the NodeJsScan scanner. Set to `true` to disable Babel processing. [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/33065) in GitLab 13.2.                                                  |
+| `SAST_DISABLE_BABEL`        | NodeJsScan | Disable Babel processing for the NodeJsScan scanner. Set to `true` to disable Babel processing. [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/33065) in GitLab 13.2.                                                  
+| `SAST_SEMGREP_METRICS` | Semgrep | Set to `"false"` to disable sending anonymized scan metrics to [r2c](https://r2c.dev/). Default: `true`. [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/330565) in GitLab 14.0.      |
 
 #### Custom CI/CD variables