We use `export default` begrudgingly here. Ideally we'd use just `export`, though this entire SDK expects things to be exported as a default. Instead of breaking everything, we'll sacrifice our export pattern for a smaller diff - a later commit can always do the default export -> regular export conversion.
The custom server path no longer shows an identity server field (for modern
homeservers), so it's confusing to have the help dialog reference it.
Part of https://github.com/vector-im/riot-web/issues/11236
