fix: cron job requires strings not int (#3994)

Author: jess-lowe

deployment/clouddeploy/gke-workers/environments/oss-vdb-test/debian-cve-convert.yaml

@@ -17,4 +17,4 @@ spec:
             - name: INPUT_GCS_BUCKET
               value: osv-test-cve-osv-conversion
             - name: NUM_WORKERS
-              value: 256
+              value: '256'