[AT-SPI] remove unnecessary lines leading to crash

[AT-SPI] remove unnecessary lines leading to crash

The eldbus_connection_unref does not mean that the connection is released.
So a signal hander of the connection should be removed if it is not used
any more.

We did not remove the signal hander but called only eldbus_connection_ref.
So there was a crash with following stack.

0  Dali::BaseSignal::Emit<Dali::Internal::Adaptor::WindowBase::AccessibilityInfo const&> (this=0x822f1b30, args#0=...) at /usr/include/dali/public-api/signals/base-signal.h:235
1  0xa4a6ca1b in Dali::Signal<void (Dali::Internal::Adaptor::WindowBase::AccessibilityInfo const&)>::Emit(Dali::Internal::Adaptor::WindowBase::AccessibilityInfo const&) (arg0=..., this=0x823b11a4) at /usr/include/dali/public-api/signals/dali-signal.h:531
2  Dali::Internal::Adaptor::WindowBaseEcoreWl2::OnEcoreElDBusAccessibilityNotification (this=0x823b1170, context=0x823b1170, message=0x820e83e0)
   at /home/abuild/rpmbuild/BUILD/dali2-adaptor-2.1.19/dali/internal/window-system/tizen-wayland/ecore-wl2/window-base-ecore-wl2.cpp:1380
3  0xa4a6ca94 in Dali::Internal::Adaptor::(anonymous namespace)::EcoreElDBusAccessibilityNotification (context=0x823b1170, message=0x820e83e0)
   at /home/abuild/rpmbuild/BUILD/dali2-adaptor-2.1.19/dali/internal/window-system/tizen-wayland/ecore-wl2/window-base-ecore-wl2.cpp:604

We do not use this signal on the AT-SPI world.
So this patch removing unnecessary lines instead of calling the
eldbus_signal_handler_del.

Change-Id: I1df91170ca9bff1e369080ccac8046954948714e