LayeredStream dtor: fully qualify 'close()' call

`close()` is a virtual function. Since we are calling it from a
destructor, make it clear that we are specifically calling the base
class (`QIODevice`) implementation, as opposed to an implementation in
any derived class.

[Found by lgtm.com](https://lgtm.com/projects/g/keepassxreboot/keepassxc/alerts)

src/streams/LayeredStream.cpp

@@ -26,7 +26,7 @@ LayeredStream::LayeredStream(QIODevice* baseDevice)
 
 LayeredStream::~LayeredStream()
 {
-    close();
+    QIODevice::close();
 }
 
 bool LayeredStream::isSequential() const