Update policy contents

Co-authored-by: Christoph Hamsen <[email protected]>

Author: sarahchen6

.github/chainguard/dd-trace-java.release.sts.yaml

@@ -9,4 +9,4 @@ claim_pattern:
   # ref: "master"
 
 permissions:
-  contents: "read,write"
+  contents: "write"