AdminAPI.InstanceController: clean up tests, rename actions

[akkoma] / test / fixtures / tesla_mock / xn--q9jyb4c_host_meta

<?xml version="1.0" encoding="UTF-8"?>
<XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0">
    <Link rel="lrdd" template="https://zetsubou.xn--q9jyb4c/.well-known/webfinger?resource={uri}" type="application/xrd+xml" />
</XRD>