Help: Update 3.9 release notes with recommended CUDA version for VS

CUDA 8.0.44 contains a bug in its VS integration that breaks
preprocessor definitions in some cases.  Recommend using at least 8.0.61
which fixes the problem.

Fixes: #16993

Help/release/3.9.rst

@@ -16,6 +16,8 @@ Languages
 * ``CUDA`` is now supported by the :ref:`Visual Studio Generators`
   for VS 2010 and above.  This complements the existing support by the
   :ref:`Makefile Generators` and the :generator:`Ninja` generator.
+  CUDA 8.0.61 or higher is recommended due to known bugs in the VS
+  integration by earlier versions.
 
 Generators
 ----------