Add PR number to whatsnew

Author: shoyer

doc/whats-new.rst

@@ -31,11 +31,11 @@ Breaking changes
   (:issue:`10654`). Previously, :py:meth:`DataTree.to_netcdf` was hard-coded to
   use h5netcdf.
   By `Stephan Hoyer <https://github.com/shoyer>`_.
-- The return value of :py:meth:`Dataset.to_netcdf` without ``path`` is
-  now a ``memoryview`` object instead of ``bytes``. This removes an unnecessary
-  memory copy and ensures consistency when using either ``engine="scipy"`` or
-  ``engine="h5netcdf"``. If you need a bytes object, simply wrap the return
-  value of ``to_netcdf()`` with ``bytes()``.
+- The return value of :py:meth:`Dataset.to_netcdf` without ``path`` is now a
+  ``memoryview`` object instead of ``bytes`` (:pull:`10656`). This removes an
+  unnecessary memory copy and ensures consistency when using either
+  ``engine="scipy"`` or ``engine="h5netcdf"``. If you need a bytes object,
+  simply wrap the return value of ``to_netcdf()`` with ``bytes()``.
   By `Stephan Hoyer <https://github.com/shoyer>`_.
 
 Deprecations