Remove one artifact restriction for DAST, SAST in docs

Fixed by
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4203

doc/user/project/merge_requests/dast.md

@@ -36,9 +36,7 @@ prerequisites:
 
 - the specified job **must** be named `dast`
 - the resulting report **must** be named `gl-dast-report.json` and uploaded as an
-  artifact. This JSON file needs to be the only artifact file for the job. If
-  you try to also include other files, it will break the vulnerability display
-  in the merge request.
+  artifact
 
 The `dast` job will perform an analysis on the running web application, the
 resulting JSON file will be uploaded as an artifact, and GitLab will then check

doc/user/project/merge_requests/sast_docker.md

@@ -30,10 +30,6 @@ In order for the report to show in the merge request, you need to specify a
 resulting `gl-sast-container-report.json` file as an artifact (exact filename).
 GitLab will then check this file and show the information inside the merge request.
 
-This JSON file needs to be the only artifact file for the job. If you try
-to also include other files, it will break the vulnerability display in the
-merge request.
-
 For more information on how the `sast:container` job should look like, check the
 example on [analyzing a Docker image for vulnerabilities][cc-docs].