QAppleKeyMapper: Print key via QKeySequence instead of as QChar

The keys map beyond the Unicode range, so we can't print them as QChar.

Luckily QKeySequence takes care of all of this for us in
QKeySequencePrivate::keyName() via QKeySequence::encodeString().

Pick-to: 6.2 6.3
Change-Id: I822c4f925854e22af5a3b4a7028cb0ed18fb67b2
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/gui/platform/darwin/qapplekeymapper.mm

@@ -551,7 +551,7 @@ const QAppleKeyMapper::KeyMap &QAppleKeyMapper::keyMapForKey(VirtualKeyCode virt
         qCDebug(lcQpaKeyMapper).verbosity(0) << "\t" << qtModifiers
             << "+" << qUtf8Printable(QString::asprintf("0x%02x", virtualKey))
             << "=" << qUtf8Printable(QString::asprintf("%d / 0x%02x /", qtKey, qtKey))
-                   << QString(QChar(qtKey));
+                   << QKeySequence(qtKey).toString();
     }
 
     return keyMap;