SystemInfo: various cleanup.

* Rename the copy slot to match naming convention elsewhere
 * Remove the Mac 10.7/10.8 detection as we don't support it now

Source/Core/DolphinQt/SystemInfo.h

@@ -21,7 +21,7 @@ public:
 	~DSystemInfo();
 
 private slots:
-	void btnCopy_pressed();
+	void CopyPressed();
 
 private:
 	std::unique_ptr<Ui::DSystemInfo> m_ui;