cocoa: remove redundant macOS version checking

Since the current minimum supported macOS version is macOS 11 (Big Sur),
we can remove redundant OS version checking and cleanup the code a bit.

Change-Id: If42251cc193e8daae81a73cb25582fa014f2b9a0
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
(cherry picked from commit 23f6d954ec5a4d9437cad433e957a718aeb9ce49)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/plugins/platforms/cocoa/qcocoadrag.mm

@@ -9,7 +9,6 @@
 #include "qcocoahelpers.h"
 #include <QtGui/private/qcoregraphics_p.h>
 #include <QtGui/qutimimeconverter.h>
-#include <QtCore/qsysinfo.h>
 #include <QtCore/private/qcore_mac_p.h>
 
 #include <vector>
@@ -137,11 +136,6 @@ bool QCocoaDrag::maybeDragMultipleItems()
     Q_ASSERT(m_drag && m_drag->mimeData());
     Q_ASSERT(m_executed_drop_action == Qt::IgnoreAction);
 
-    if (QOperatingSystemVersion::current() < QOperatingSystemVersion::MacOSMojave) {
-        // -dragImage: stopped working in 10.14 first.
-        return false;
-    }
-
     const QMacAutoReleasePool pool;
 
     NSView *view = m_lastView ? m_lastView : m_lastEvent.window.contentView;

src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm

@@ -14,8 +14,6 @@
 #include <QtCore/qstringlist.h>
 #include <QtCore/qvarlengtharray.h>
 #include <QtCore/qabstracteventdispatcher.h>
-#include <QtCore/qsysinfo.h>
-#include <QtCore/qoperatingsystemversion.h>
 #include <QtCore/qdir.h>
 #include <QtCore/qregularexpression.h>
 #include <QtCore/qpointer.h>

src/plugins/platforms/cocoa/qcocoatheme.mm

@@ -5,7 +5,6 @@
 
 #include "qcocoatheme.h"
 
-#include <QtCore/QOperatingSystemVersion>
 #include <QtCore/QVariant>
 
 #include "qcocoasystemtrayicon.h"
@@ -214,12 +213,10 @@ const char *QCocoaTheme::name = "cocoa";
 QCocoaTheme::QCocoaTheme()
     : m_systemPalette(nullptr)
 {
-    if (QOperatingSystemVersion::current() >= QOperatingSystemVersion::MacOSMojave) {
     m_appearanceObserver = QMacKeyValueObserver(NSApp, @"effectiveAppearance", [this] {
         NSAppearance.currentAppearance = NSApp.effectiveAppearance;
         handleSystemThemeChange();
     });
-    }
 
     m_systemColorObserver = QMacNotificationObserver(nil,
         NSSystemColorsDidChangeNotification, [this] {

src/plugins/platforms/cocoa/qnsview.mm

@@ -21,7 +21,6 @@
 #include <QtCore/QDebug>
 #include <QtCore/QPointer>
 #include <QtCore/QSet>
-#include <QtCore/qsysinfo.h>
 #include <QtCore/private/qcore_mac_p.h>
 #include <QtGui/QAccessible>
 #include <QtGui/QImage>

src/plugins/platforms/cocoa/qnsview_gestures.mm

@@ -11,9 +11,6 @@ Q_LOGGING_CATEGORY(lcQpaGestures, "qt.qpa.input.gestures")
 
 - (bool)handleGestureAsBeginEnd:(NSEvent *)event
 {
-    if (QOperatingSystemVersion::current() < QOperatingSystemVersion::OSXElCapitan)
-        return false;
-
     if ([event phase] == NSEventPhaseBegan) {
         [self beginGestureWithEvent:event];
         return true;

src/plugins/platforms/cocoa/qnswindow.mm

@@ -12,7 +12,6 @@
 #include "qcocoaintegration.h"
 
 #include <qpa/qwindowsysteminterface.h>
-#include <qoperatingsystemversion.h>
 
 Q_LOGGING_CATEGORY(lcQpaEvents, "qt.qpa.events");