docs: replace old Rinkeby reference

[dcroote]

The main purpose of this PR is to add a changeset so that the Docker build step of CI stops failing (see #1585 (comment))

[Siegrift]

👍 LGTM, but how did this error happen in the first place 🤔 ?

[dcroote]

how did this error happen in the first place 🤔 ?

Do you mean why does the absence of a changeset cause CI failure? Or why was there a Rinkeby reference in the README? If the former, this has existed for some time, but only crops up after a release followed by a PR without a changeset. If the latter, I'm guessing when other references to Rinkeby were being removed, this README instance was missed.

[Siegrift]

Yeah I meant the former. I still don't understand this:

but only crops up after a release followed by a PR without a changeset

We have a check that ensures that every PR has a changeset (even empty one). So we should not have this issue 🤔

[dcroote]

We have a check that ensures that every PR has a changeset

Except for Renovate PRs, which is what I happened to merge first after the 0.14 release 🙃