Update walkthrough.md

[sysintelligent]

Provide extra instruction for using Helm v3 when installing and deleting mini broker.

This PR is a

• [ ] Feature Implementation
• [ ] Bug Fix
• [x] Documentation

What this PR does / why we need it:

For Helm v3, the commands in the walkthrough for installing and deleting minibroker will exit with an error message.

Which issue(s) this PR fixes

Fixes #

Please leave this checklist in the PR comment so that maintainers can ensure a good PR.

Merge Checklist:

• [ ] New feature
  • [ ] Tests
  • [ ] Documentation
• [ ] SVCat CLI flag
• [ ] Server Flag for config
  • [ ] Chart changes
  • [ ] removing a flag by marking deprecated and hiding to avoid breaking the chart release and existing clients who provide a flag that will get an error when they try to update

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[k8s-ci-robot]

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[k8s-ci-robot]

Hi @sysintelligent. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[sysintelligent]

Thanks for your pull request. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

Please follow instructions at https://git.k8s.io/community/CLA.md#the-contributor-license-agreement to sign the CLA.

It may take a couple minutes for the CLA signature to be fully registered; after that, please reply here with a new comment and we'll verify. Thanks.

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please sign in with your organization's credentials at https://identity.linuxfoundation.org/projects/cncf to be authorized.
• If you have done the above and are still having issues with the CLA being reported as unsigned, please log a ticket with the Linux Foundation Helpdesk: https://support.linuxfoundation.org/
• Should you encounter any issues with the Linux Foundation Helpdesk, send a message to the backup e-mail support address at: login-issues@jira.linuxfoundation.org

Signed.

[piotrmiskiewicz]

/ok-to-test

[piotrmiskiewicz]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: piotrmiskiewicz, sysintelligent

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

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/kubernetes-sigs/service-catalog/blob/master/OWNERS)~~ [piotrmiskiewicz] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[piotrmiskiewicz]

/test pull-service-catalog-test-integration

[piotrmiskiewicz]

/test pull-service-catalog-test-integration

[sysintelligent]

/test pull-service-catalog-test-integration

[piotrmiskiewicz]

/test pull-service-catalog-test-integration

[piotrmiskiewicz]

/test pull-service-catalog-test-integration

[jhvhs]

/test pull-service-catalog-test-integration

[jhvhs]

/lgtm