Fix hardcoded knative-eventing namespace in eventingControllerSAName

[vaidikcode]

Fixes #8407

Proposed Changes

-:bug: Fix bug

• changed the hardcoded value as discussed in Unable to deploy eventing in different namespace because of hardcoded namespace #8407

Pre-review Checklist

• At least 80% unit test coverage
• E2E tests for any new behavior
• Docs PR for any user-facing impact
• Spec PR for any new API feature
• Conformance test for any change to the spec

Release Note

Docs

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: vaidikcode
Once this PR has been reviewed and has the lgtm label, please assign dsimansk for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[knative-prow]

Hi @vaidikcode. Thanks for your PR.

I'm waiting for a knative member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[pierDipi]

https://github.com/knative/eventing/actions/runs/12930925415/job/36063811420?pr=8425

Various

panic: The environment variable "SYSTEM_NAMESPACE" is not set
	
	If this is a process running on Kubernetes, then it should be using the downward
	API to initialize this variable via:
	
	  env:
	  - name: SYSTEM_NAMESPACE
	    valueFrom:
	      fieldRef:
	        fieldPath: metadata.namespace

We would need to update the tests

[vaidikcode]

How should we approach this? Should I keep it simple with:

var eventingControllerSAName = fmt.Sprintf("system:serviceaccount:%s:eventing-controller", system.Namespace())

Should I also start working on tests?