Improve e2e test

Currently, the e2e test fails when the following two resources already exist:
```
Error from server (AlreadyExists): error when creating "STDIN": customresourcedefinitions.apiextensions.k8s.io "remotes.gitkube.sh" already exists
Error from server (AlreadyExists): error when creating "STDIN": clusterrolebindings.rbac.authorization.k8s.io "gitkube" already exists
```
For the CRD, we just need to ignore the error and for clusterrolebindings we can just use the test namespace name.

Start by locating the e2e test setup that creates the Kubernetes CRD and clusterrolebinding. Reproduce the failure with those resources already present, then verify the test handles the existing CRD and uses the test namespace in the binding name. Done means the e2e test passes in both clean and pre-existing-resource environments.

Written by the indexing model from the issue text.