GUI: accessible - silence clang's fallthrough warning

Pick-to: 6.7
Change-Id: I868aee05315e1258a8872137407a0c5132251c71
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>
(cherry picked from commit f91aebaa3f2a11b5681d8c9fa18c69d2ddd0da05)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/gui/accessible/linux/qspiapplicationadaptor.cpp

@@ -165,6 +165,7 @@ bool QSpiApplicationAdaptor::eventFilter(QObject *target, QEvent *event)
             keyEvents.enqueue(QPair<QPointer<QObject>, QKeyEvent*> (QPointer<QObject>(target), copyKeyEvent(keyEvent)));
             return true;
         }
+        break;
     }
     default:
         break;