System removed support for redis namespaces, check this issue: https://issues.redhat.com/browse/THREESCALE-10213

Redis namespaces seem to not be used anymore from the operator, however, there are references to it in the code. like here:

$ rg REDIS_NAMESPACE
pkg/3scale/amp/component/system.go
167: helper.EnvVarFromSecret("REDIS_NAMESPACE", SystemSecretSystemRedisSecretName, SystemSecretSystemRedisNamespace),

The REDIS_NAMESPACE env variable is going to be ignored by system from now on. Any reference to this variable or any code related to redis namespaces is dead code now and should be cleaned up.