Use preference value for Gitpod endpoint everywhere

[mads-hartmann]

Following up on https://github.com/raycast/extensions/pull/5457 - the changes are different here as the code-bases have diverged, but the intention is the same. Most of the work was already done in this repository, so I just grep'ed for the remaining hardcoded references to gitpod.io and changed them to use the preference value instead. ☺️

I did some very basic testing of this:

npm run build # Just to check that I didn't break the build
npm run dev   # To install the extension
# Change the preference value to our Gitpod-internal dogfooding endpoint
# Opened a workspace to ensure it did indeed use endpoint (it did)

[Palanikannan1437]

LGTM 🍊, thanks for fixing this for the remaining references 🚀

Especially for taking out the time for making the PR again for this repository 🙈🧡