gitlab provided $KUBECONFIG in ci is not following $KUBE_NAMESPACE
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### Summary
kubernetes account provided in KUBECONFIG is not in the right namespace when setting namespace with KUBE_NAMESPACE in CI settings
### Steps to reproduce
Add a RBAC enabled kubernetes cluster to your project
Set up $KUBE_NAMESPACE to whatever existing namespace in your kubernetes cluster.

set up a CI stage with an environment :

and try to apply a file in the cluster :
kubectl apply -f ./file.yml --namespace $KUBE_NAMESPACE
### What is the current *bug* behavior?

user provided in $KUBECONFIG has no edit right in the $KUBE_NAMESPACE

and $KUBECONFIG content :

### What is the expected *correct* behavior?

namespace should be $KUBE_NAMESPACE
and this token should have edit rights in $KUBE_NAMESPACE
### Relevant logs and/or screenshots
see previous screenshots
### Output of checks
This bug happens on GitLab.com
#### Results of GitLab environment info
This bug happens on GitLab.com
#### Results of GitLab application Check
This bug happens on GitLab.com
### Possible fixes
issue