ci: remove signpath policy

.signpath/policies/opencode/test-signing.yml

@@ -1,7 +0,0 @@
-github-policies:
-  runners:
-    allowed_groups:
-      - "blacksmith runners 01kbd5v56sg8tz7rea39b7ygpt"
-  build:
-    disallow_reruns: false
-  branch_rulesets: