HoldTillRename: Rename knative-sandbox to knative-extension

[davidhadas]

This is an automated PR to replace knative-sandbox strings to knative-extension. Do not merge until productivity renames knative-sandbox org to knative-extension.

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: davidhadas
Once this PR has been reviewed and has the lgtm label, please assign nainaz for approval. For more information see the Kubernetes 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]

@davidhadas: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-knative-sandbox-peribolos	de9ff04	link	true	/test pull-knative-sandbox-peribolos

Your PR dashboard.

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/test-infra repository. I understand the commands that are listed here.

[knative-prow-robot]

PR needs rebase.

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/test-infra repository.

[davidhadas]

replaced to extensions