Update Gitpod integration docs

What does this MR do and why?

This will update the Gitpod integration screenshot in the relevant docs as Gitpod no longer uses Theia, but VS Code.

This will follow also what exists also in the GDK in Gitpod instructions, see relevant docs.

Dropped the image in docs and made a small rephrase.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.