Remove duplicate text in os documentation.
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index d8ab8b7..5737755 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -29,11 +29,6 @@
objects, and result in an object of the same type, if a path or file name is
returned.
-.. note::
-
- If not separately noted, all functions that claim "Availability: Unix" are
- supported on Mac OS X, which builds on a Unix core.
-
* An "Availability: Unix" note means that this function is commonly found on
Unix systems. It does not make any claims about its existence on a specific
operating system.