message: [dbus] remove legacy feature guard
  The OpenThread stack will return error flags when this feature is not
  enabled.
diff: #include <openthread/instance.h>
  #include <openthread/joiner.h>
  #include <openthread/link_raw.h>
  +#include <openthread/ncp.h>
  #include <openthread/netdata.h>
  #include <openthread/thread_ftd.h>
  #include <openthread/platform/radio.h>
  @@ -431,12 +432,8 @@ exit:
  return err;
  }
  -#if OPENTHREAD_CONFIG_LEGACY_ENABLE
  -extern "C" void otNcpHandleDidReceiveNewLegacyUlaPrefix(const uint8_t *aUlaPrefix);
  -#endif
  otError DBusThreadObject::SetLegacyUlaPrefixHandler(DBusMessageIter &aIter)
  {
  -#if OPENTHREAD_CONFIG_LEGACY_ENABLE
  std::array<uint8_t, OTBR_IP6_PREFIX_SIZE> data;
  otError err = OT_ERROR_NONE;
  @@ -445,9 +442,6 @@ otError DBusThreadObject::SetLegacyUlaPrefixHandler(DBusMessageIter &aIter)
  exit:
  return err;
  -#else
  - return OT_ERROR_NOT_IMPLEMENTED;
  -#endif // OPENTHREAD_CONFIG_LEGACY_ENABLE
  }
  otError DBusThreadObject::SetLinkModeHandler(DBusMessageIter &aIter)
  