removing aws cred placeholders, no longer needed

cron/backup.conf

@@ -1,7 +1,5 @@
 [options]
 esservers=http://localhost:9200
-aws_access_key_id = <add_aws_access_key_id>
-aws_secret_access_key = <add_aws_secret_access_key>
 aws_bucket = <add_s3_bucket_name>
 backup_indices = <add_backup_indices>
 backup_dobackup = 1,1,1,1,1,1,1,1