ProjectExplorer: Base IDevice::osType on a data member

Change-Id: I969563e6e62895a51fb4692c8eb0bab278f0ecae
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/ios/iosdevice.h

@@ -59,7 +59,6 @@ public:
     QString osVersion() const;
     Utils::Port nextPort() const;
     bool canAutoDetectPorts() const override;
-    Utils::OsType osType() const override;
 
     static QString name();