It seems you’re connecting to a redis server which requires authentication, but you aren’t providing any.
Assuming redis is in a safe environment, you can disable the authentication mechanism in the redis server to allow anyone to connect. Of course, you should ensure that only ownCloud can access to that redis server.
If you still want to authenticate against the redis server, you can try the following configuration:
'redis' => [
'host' => 'localhost',
'port' => 6379,
'password' => [
'user' => 'username',
'pass' => 'password'
],
],
or
'redis' => [
'host' => 'localhost',
'port' => 6379,
'password' => 'password',
],