Simplify cleanup task

[afrittoli]

Changes

The "--keep" option in tkn does not require "--all" anymore
since tkn v0.9.0, so removing that.

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Includes docs (if user facing)
• Commit messages follow commit message best practices

See the contribution guide
for more details.

/kind cleanup

[afrittoli]

/cc @danielhelfand

[tekton-robot]

This PR cannot be merged: expecting exactly one kind/ label

Available kind/ labels are:

kind/bug: Categorizes issue or PR as related to a bug.
kind/flake: Categorizes issue or PR as related to a flakey test
kind/cleanup: Categorizes issue or PR as related to cleaning up code, process, or technical debt.
kind/design: Categorizes issue or PR as related to design.
kind/documentation: Categorizes issue or PR as related to documentation.
kind/feature: Categorizes issue or PR as related to a new feature.
kind/misc: Categorizes issue or PR as a miscellaneuous one.

[danielhelfand]

/lgtm

[vdemeester]

/meow

[tekton-robot]

@vdemeester:

In response to this:

/meow

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.

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: vdemeester

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

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [vdemeester]

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