[Docs] Self-Hosted: Cloud Upgrade Instructions

#### Current State
Instructions for greenfield deployments exists on the https://docs.layer5.io/cloud/self-hosted/ pages.

#### Desired State
The https://docs.layer5.io/cloud/self-hosted/ pages are in need of upgrade instructions for existing Layer5 Cloud deployments.

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#### [Contributor Guides](https://docs.meshery.io/project/contributing) and Resources
- 📚 [Instructions for contributing to documentation](https://docs.meshery.io/project/contributing/contributing-docs)
- Meshery documentation [site](https://docs.meshery.io/) and [source](https://github.com/meshery/meshery/tree/master/docs)
- 🛠 [Meshery Build & Release Strategy](https://docs.meshery.io/project/build-and-release)
- 🎨 Wireframes and [designs for Layer5 site](https://www.figma.com/file/5ZwEkSJwUPitURD59YHMEN/Layer5-Designs) in Figma [(open invite)](https://www.figma.com/team_invite/redeem/qJy1c95qirjgWQODApilR9)
- 🙋🏾🙋🏼 Questions: [Layer5 Discussion Forum](https://discuss.layer5.io) and [Layer5 Community Slack](http://slack.layer5.io)