__nextcloud: harden here-doc for su call

Because the here-doc will be evaluated again by the shell, it will was
changed to avoid this. Because the script does not depend on such
function, it will be done in faviour of special characters.

type/__nextcloud/gencode-remote

@@ -16,7 +16,7 @@ occ() {
     # su creates a new shell, so it does not affect the current session
     #  will not use -q as it supresses errors, too
     cat << SHELL
-su -s /bin/sh -l "$user" -- -e <<SU
+su -s /bin/sh -l "$user" -- -e <<'SU'
 cd '$installdir' && php occ --no-warnings --no-interaction --no-ansi $@
 SU
 SHELL