message: Fix DOM nesting error in cross-signing panel
  The spinner can't be inside a `<p>` element. This also changes to block spinner
  to match key backup.
diff: @@ -163,8 +163,8 @@ export default class CrossSigningPanel extends React.PureComponent {
  let summarisedStatus;
  if (homeserverSupportsCrossSigning === undefined) {
  - const InlineSpinner = sdk.getComponent('views.elements.InlineSpinner');
  - summarisedStatus = <p><InlineSpinner /></p>;
  + const Spinner = sdk.getComponent('views.elements.Spinner');
  + summarisedStatus = <Spinner />;
  } else if (!homeserverSupportsCrossSigning) {
  summarisedStatus = <p>{_t(
  "Your homeserver does not support cross-signing.",
  