macOS: don't block CMD+H while a popup is open

The shortcut hides the application, which works in native apps such as
Xcode or Safari also while a popup menu (or combobox drop down) is open.

This essentially reverts 29104c85db, which
introduced the blocking of CMD+H to prevent the popup stack in the Cocoa
plugin from going out of sync. With that stack gone after the previous
commits, this is no longer a problem.

Task-number: QTBUG-82626
Task-number: QTBUG-96450
Task-number: QTBUG-58727
Pick-to: 6.2
Change-Id: I35603d971741f03b793b7839b183b7ab37200647
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/plugins/platforms/cocoa/qcocoamenuloader.mm

@@ -320,13 +320,8 @@
 - (BOOL)validateMenuItem:(NSMenuItem*)menuItem
 {
     if (menuItem.action == @selector(hideOtherApplications:)
-        || menuItem.action == @selector(unhideAllApplications:))
-        return [NSApp validateMenuItem:menuItem];
-
-    if (menuItem.action == @selector(hide:)) {
-        auto *w = QCocoaIntegration::instance()->activePopupWindow();
-        if (w && (w->window()->type() != Qt::ToolTip))
-            return NO;
+        || menuItem.action == @selector(unhideAllApplications:)
+        || menuItem.action == @selector(hide:)) {
         return [NSApp validateMenuItem:menuItem];
     }