Run e2e tests after rebrand to Upsun

Platform.sh has rebranded to Upsun.

- [x] Does this plugin still work? Run e2e test. (Still passes.)
- [x] How can I access a dashboard to see deployed resources? (No idea without making an Upsun account, and this looks like a flat $9/mo project fee (not prorated), plus $10/mo per user, plus resources. This is an entirely different pricing model to develop against.) (existing credentials work on Upsun.)
- [x] Open a support request to clarify pricing. (Reached out through contact form, copied text of message in offline notes.)
- [ ] How can we transition to an Upsun plugin? Is there any reason to keep Upsun in the dsd org if its pricing is way out of bounds for people learning deployment?