Update: ruby-gdk_pixbuf2 4.1.7

[Daisuke Fujimura via Cygwin-announce]

The following packages have been uploaded to the Cygwin distribution:

- https://cygwin.com/packages/summary/ruby-gdk_pixbuf2-src.html
  - ruby-gdk_pixbuf2
  - ruby-gdk_pixbuf2-doc