Re-enable register button on change to working HS
Re-enable register button on change to working HS

Register button disabling is done via serverErrorIsFatal so we need
to reset this on a successful validation.

https://github.com/vector-im/riot-web/issues/10029

matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk