fix: typo in entrypoint file

Author: Ben Honda

backwork/docker-entrypoint.sh

@@ -192,7 +192,7 @@ back_up_mongo() {
     return
   fi
 
-  if [[ -z "${MONGO_URI}" ]]
+  if [[ -z "${MONGO_HOST}" ]]
   then
     echo "MONGO_HOST is not specified, skipping."
   else