Just re-use the OSH service account

The pipeline clearup seems to work but taskrun clearup fails for some
reason

```
All but 10 PipelineRuns(Completed) deleted in namespace "pct-security-tooling"
Error: failed to delete TaskRun "osh-scan-scm-taskrun-test-pjtvw":
taskruns.tekton.dev "osh-scan-scm-taskrun-test-pjtvw" is forbidden: User
"system:serviceaccount:pct-security-tooling:osh" cannot delete resource
"taskruns" in API group "tekton.dev" in the namespace
"pct-security-tooling"; failed to delete TaskRun
"osh-scan-scm-taskrun-test-9gx7z": taskruns.tekton.dev
"osh-scan-scm-taskrun-test-9gx7z" is forbidden: User
"system:serviceaccount:pct-security-tooling:osh" cannot delete resource
"taskruns" in API group "tekton.dev" in the namespace
"pct-security-tooling"; failed to delete TaskRun
"osh-scan-scm-taskrun-test-g7vlh": taskruns.tekton.dev
"osh-scan-scm-taskrun-test-g7vlh" is forbidden: User
"system:serviceaccount:pct-security-tooling:osh" cannot delete resource
"taskruns" in API group "tekton.dev" in the namespace
"pct-security-tooling"; ....
```

k8s/stage/osh-client-tekton/tekton-cleanup-cronjob.yaml

@@ -10,6 +10,7 @@ spec:
     spec:
       template:
         spec:
+          serviceAccountName: osh
           containers:
           - name: tekton-cleanup
             image: quay.io/openshift-pipeline/openshift-pipelines-cli-tkn:1.11
@@ -17,5 +18,5 @@ spec:
             command:
             - /bin/sh
             - -c
-            - tkn pipelinerun delete --keep 10 && tkn taskrun delete --keep 20
-          restartPolicy: OnFailure
+            - tkn pipelinerun delete --keep 10 -f && tkn taskrun delete --keep 20 -f
+          restartPolicy: Never