fix(openapi): update openapi server url

[DominikB2014]

Since we moved to regional apis, our server url is now us.sentry.io.

Someone can correct me if i'm wrong, but the europe server url is de.sentry.io? In which case, we can add it as well.

For context, when you feed the api spec into a doc generator such as swagger UI, the server url is used as a base url to all the endpoints.