add sign-off parameter to cncf conformance pr script

Signed-off-by: hendrikKahl <hendrik.kahl@sap.com>

cmd/cncf-conformance-pr-creator/create_pr_k8s_conformance.py

@@ -289,7 +289,7 @@ def commitAndPushChanges(gitHelper, branch_name):
     subprocess.run(["git", "add", "*e2e.log"])
     subprocess.run(["git", "add", "*junit_01.xml"])
     subprocess.run(["git", "add", "*README.md"])
-    subprocess.run(["git", "commit", "-m", "gardener supporting new k8s release"])
+    subprocess.run(["git", "commit", "-s",  "-m", "gardener supporting new k8s release"])
     gitHelper.push("@", f"refs/heads/{branch_name}")
     # subprocess.run(["git", "push", "origin", branch_name])
     print('Branch "' + branch_name + '" was successfully created on https://github.com/' +