Fix: postgres-backup-s3 crontab syntax

It was yielding an error "user lookup failed: user: unknown user
/bin/sh"

Author: matiasgarciaisaia

postgres-backup-s3/run.sh

@@ -9,6 +9,6 @@ fi
 if [ "${SCHEDULE}" = "**None**" ]; then
   sh backup.sh
 else
-  echo -e "SHELL=/bin/sh\n${SCHEDULE} /bin/sh /backup.sh" > /etc/crontabs/root
+  echo -e "SHELL=/bin/sh\n${SCHEDULE} root /bin/sh /backup.sh" > /etc/crontabs/root
   exec go-crond /etc/crontabs/root
 fi