Remove SeatInterface::keyboardCreated signal

It's pointless with the new design.

src/wayland/autotests/client/test_wayland_seat.cpp

@@ -1496,9 +1496,6 @@ void TestWaylandSeat::testKeyboard()
     SurfaceInterface *serverSurface = surfaceCreatedSpy.first().first().value<KWaylandServer::SurfaceInterface*>();
     QVERIFY(serverSurface);
 
-    QSignalSpy keyboardCreatedSpy(m_seatInterface,  &SeatInterface::keyboardCreated);
-    QVERIFY(keyboardSpy.isValid());
-
     Keyboard *keyboard = m_seat->createKeyboard(m_seat);
     QSignalSpy repeatInfoSpy(keyboard, &Keyboard::keyRepeatChanged);
     QVERIFY(repeatInfoSpy.isValid());
@@ -1507,7 +1504,6 @@ void TestWaylandSeat::testKeyboard()
     QCOMPARE(keyboard->isKeyRepeatEnabled(), false);
     QCOMPARE(keyboard->keyRepeatDelay(), 0);
     QCOMPARE(keyboard->keyRepeatRate(), 0);
-    QVERIFY(keyboardCreatedSpy.wait());
     QVERIFY(repeatInfoSpy.wait());
     wl_display_flush(m_connection->display());
     QTest::qWait(100);

src/wayland/seat_interface.cpp

@@ -479,7 +479,6 @@ void SeatInterface::Private::getKeyboard(wl_client *client, wl_resource *resourc
     }
 
     keyboard->d->add(client, id, wl_resource_get_version(resource));
-    emit q->keyboardCreated(keyboard.data());
 }
 
 void SeatInterface::Private::getTouchCallback(wl_client *client, wl_resource *resource, uint32_t id)

src/wayland/seat_interface.h

@@ -653,8 +653,6 @@ Q_SIGNALS:
     void touchMoved(qint32 id, quint32 serial, const QPointF &globalPosition);
     void timestampChanged(quint32);
 
-    void keyboardCreated(KWaylandServer::KeyboardInterface*);
-
     /**
      * Emitted whenever the selection changes
      * @since 5.56