Fix fallthough in CodeView/MemoryView widgets

This slightly changes the behaviour, but I think this is more correct.

Source/Core/DolphinQt/Debugger/CodeViewWidget.cpp

@@ -1174,7 +1174,9 @@ void CodeViewWidget::keyPressEvent(QKeyEvent* event)
     if (event->modifiers() == Qt::ControlModifier)
     {
       emit ActivateSearch();
+      return;
     }
+    [[fallthrough]];
   default:
     QWidget::keyPressEvent(event);
     break;

Source/Core/DolphinQt/Debugger/MemoryViewWidget.cpp

@@ -126,7 +126,9 @@ public:
       if (event->modifiers() == Qt::ControlModifier)
       {
         m_view->TriggerActivateSearch();
+        return;
       }
+      [[fallthrough]];
     default:
       QWidget::keyPressEvent(event);
       return;