[stable/gitlab-ce,ee] Add deprecation note in favor of official Charts

[lambertjosh]

GitLab provides a set of official charts. These charts are actively being developed, and are planned to be added to this repo soon. In the interim, we should inform users that they may want to consider those charts to get started.

Fixes #1138

[k8s-ci-robot]

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://github.com/kubernetes/kubernetes/wiki/CLA-FAQ 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 email the CNCF helpdesk: helpdesk@rt.linuxfoundation.org

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.

[k8s-ci-robot]

Hi @lambertjosh. Thanks for your PR.

I'm waiting for a kubernetes 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.

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

[lambertjosh]

Signed the CLA.

[prydonius]

@lambertjosh can we add deprecated: true to the Chart.yaml files? See https://docs.helm.sh/developing_charts/#deprecating-charts

[lambertjosh]

Thanks @prydonius, I've added the deprecated: true flag as well as updated the NOTES.txt to include a warning as well.

[unguiculus]

/lgtm