Make this a note again.

Doc/library/test.rst

@@ -5,7 +5,7 @@
    :synopsis: Regression tests package containing the testing suite for Python.
 .. sectionauthor:: Brett Cannon <brett@python.org>
 
-.. warning::
+.. note::
    The :mod:`test` package is meant for internal use by Python only. It is
    documented for the benefit of the core developers of Python. Any use of
    this package outside of Python's standard library is discouraged as code