Change the name/key of the style to 'macos'. Besides the
name 'macintosh' being archaic, we also need this
change to avoid creating 'macintosh' style folders
in QtQuickControls, now that we plan to use QPlatformTheme
also there to resolve the style.
[ChangeLog][Widgets][QStyle] The 'macintosh' style
has been renamed to 'macos'.
Change-Id: I14b8a8b4dbd369e7a7d16b94e4ad27e501e7e8d0
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>