QCocoaWindow - fix a compilation error

Clang does not like Q_FALLTHROUGH in 'default' label, the diagnostics is:
'fallthrough annotation does not directly precede switch label'.
Accodring to their docs: "The fallthrough (or clang::fallthrough) attribute
is used to annotate intentional fall-through between switch labels. It can
only be applied to a null statement placed at a point of execution between
any statement and the next switch label." - obviously, there is no 'next
switch label' in our case.

Change-Id: Ia7dba4cb965a85d229d44b04b69633a8f07d4a0c
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -1867,8 +1867,7 @@ void QCocoaWindow::applyWindowState(Qt::WindowState newState)
         // the new state.
         return;
     }
-    default:
-        Q_FALLTHROUGH();
+    default:;
     }
 
     // Then we apply the new state if needed
@@ -1886,12 +1885,8 @@ void QCocoaWindow::applyWindowState(Qt::WindowState newState)
         [m_nsWindow miniaturize:sender];
         break;
     case Qt::WindowNoState:
-        switch (windowState()) {
-        case Qt::WindowMaximized:
+        if (windowState() == Qt::WindowMaximized)
             toggleMaximized();
-        default:
-            Q_FALLTHROUGH();
-        }
         break;
     default:
         Q_UNREACHABLE();