Add a new policy to .gitlab/security-policies/policy.yml

.gitlab/security-policies/policy.yml

+---
+scan_execution_policy:
+- name: greyhound
+  description: yyy
+  enabled: true
+  rules:
+  - type: pipeline
+    branches:
+    - main
+  actions:
+  - scan: secret_detection
+approval_policy: []