message: Fix key backup trust text for cross-signing
  This fixes the key backup panel to use the correct object when checking whether
  a device is verified or unverified via cross-signing trust.
diff: @@ -277,25 +277,25 @@ export default class KeyBackupPanel extends React.PureComponent {
  "Backup has an <validity>invalid</validity> signature from this session",
  {}, { validity },
  );
  - } else if (sig.valid && sig.device.isVerified()) {
  + } else if (sig.valid && sig.deviceTrust.isVerified()) {
  sigStatus = _t(
  "Backup has a <validity>valid</validity> signature from " +
  "<verify>verified</verify> session <device></device>",
  {}, { validity, verify, device },
  );
  - } else if (sig.valid && !sig.device.isVerified()) {
  + } else if (sig.valid && !sig.deviceTrust.isVerified()) {
  sigStatus = _t(
  "Backup has a <validity>valid</validity> signature from " +
  "<verify>unverified</verify> session <device></device>",
  {}, { validity, verify, device },
  );
  - } else if (!sig.valid && sig.device.isVerified()) {
  + } else if (!sig.valid && sig.deviceTrust.isVerified()) {
  sigStatus = _t(
  "Backup has an <validity>invalid</validity> signature from " +
  "<verify>verified</verify> session <device></device>",
  {}, { validity, verify, device },
  );
  - } else if (!sig.valid && !sig.device.isVerified()) {
  + } else if (!sig.valid && !sig.deviceTrust.isVerified()) {
  sigStatus = _t(
  "Backup has an <validity>invalid</validity> signature from " +
  "<verify>unverified</verify> session <device></device>",
  