Fix RO update check

Author: thespad

root/etc/s6-overlay/s6-rc.d/init-plex-update/run

@@ -1,7 +1,7 @@
 #!/usr/bin/with-contenv bash
 # shellcheck shell=bash
 
-if [[ -z ${LSIO_READ_ONLY_FS} ]] || [[ -z ${LSIO_NON_ROOT_USER} ]]; then
+if [[ -n ${LSIO_READ_ONLY_FS} ]] || [[ -n ${LSIO_NON_ROOT_USER} ]]; then
     echo "Runtime update not supported with read-only or non-root operation, skipping."
     exit 0
 fi