Win installer: Stop adding the "Uninstall Krita" item to the Start Menu

The "Uninstall Krita" start menu item is mostly redundant since users
can perform the uninstallation from the Control Panel. Windows 10 also
offers to open the relevant Settings page when users right-click on the
Krita icon and select "Uninstall". Moreover, recent Windows 10 versions
automatically hides the "Uninstall Krita" menu item (but would fail to
do so if its name is localized).