DeprecationRequest: Remove Gitpod Support

[kenibrewer]

The past few months I've switched exclusively to coding in Codespaces or the local DevContainer and haven't verified if the Gitpod dev environment is still functioning correctly.

I propose we remove the gitpod configuration because the extra maintenance burden of maintaining two cloud dev environments doesn't seem worth the cost for a small project like ours.

The Codespaces / Devcontainer option has the advantage of including both a local and cloud-based environment with a single definition file. Beyond that, the original rationale for including GitPod to support a open-source competitor of Microsoft is less true now that the company Gitpod has deprecated support for the open source deployments of their product.