Adding docs for new api fuzzing plan limits db column

doc/administration/instance_limits.md

@@ -333,6 +333,7 @@ setting is used:
 | Artifact limit name                         | Default value |
 |---------------------------------------------|---------------|
 | `ci_max_artifact_size_accessibility`        | 0             |
+| `ci_max_artifact_size_api_fuzzing`          | 0             |
 | `ci_max_artifact_size_archive`              | 0             |
 | `ci_max_artifact_size_browser_performance`  | 0             |
 | `ci_max_artifact_size_cluster_applications` | 0             |