Fix note markup (#16805).

Patch by Tshepang Lekhonkhobe, reviewed by Georg Brandl.
diff --git a/Doc/library/test.rst b/Doc/library/test.rst
index c1270f4..c28536d 100644
--- a/Doc/library/test.rst
+++ b/Doc/library/test.rst
@@ -199,6 +199,7 @@
 test suite.
 
 .. note::
+
    :mod:`test.support` is not a public module.  It is documented here to help
    Python developers write tests.  The API of this module is subject to change
    without backwards compatibility concerns between releases.