DOC: remove reference to OpenSolaris (python#102671)

Author: partev

Doc/using/unix.rst

@@ -54,13 +54,6 @@ On FreeBSD and OpenBSD
      pkg_add ftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/i386/python-2.5.1p2.tgz
 
 
-On OpenSolaris
---------------
-
-You can get Python from `OpenCSW <https://www.opencsw.org/>`_.  Various versions
-of Python are available and can be installed with e.g. ``pkgutil -i python27``.
-
-
 .. _building-python-on-unix:
 
 Building Python