Fix pattern matching in dd-octo-sts policy (#10174)

* Fix pattern matching in dd-octo-sts policy

Author: sarahchen6

.github/chainguard/self.pin-system-tests.create-pr.sts.yaml

@@ -1,11 +1,11 @@
 issuer: https://token.actions.githubusercontent.com
 
-subject_pattern: repo:DataDog/dd-trace-java:ref:refs/heads/*
+subject_pattern: ^repo:DataDog/dd-trace-java:ref:refs/heads/.+$
 
 claim_pattern:
   event_name: (push|workflow_dispatch)
-  ref: refs/heads/*
-  job_workflow_ref: DataDog/dd-trace-java/\.github/workflows/pin-system-tests\.yaml@refs/heads/master
+  ref: refs/heads/.+
+  job_workflow_ref: DataDog/dd-trace-java/\.github/workflows/pin-system-tests\.yaml@refs/heads/.+
 
 permissions:
   contents: write