whatsnew: summary section tweaks.

Removed an entry made redundant by the new security section,
Moved 'marshal' to the section on features other platforms
will need to support, and mention that 'help' is improved
by the inspect/pydoc changes (#19561 msg213153).

Doc/whatsnew/3.4.rst

@@ -100,6 +100,8 @@ New expected features for Python implementations:
   that are not text encodings (multiple issues).
 * :ref:`A ModuleSpec Type <whatsnew-pep-451>` for the Import System
   (:pep:`451`).  (Affects importer authors.)
+* The :mod:`marshal` format has been made :ref:`more compact and efficient
+  <whatsnew-marshal-3>` (:issue:`16475`).
 
 New library modules:
 
@@ -131,7 +133,8 @@ Significantly Improved Library Modules:
   (:class:`~email.contentmanager.EmailMessage`) that :ref:`simplify MIME
   handling <whatsnew_email_contentmanager>` (:issue:`18891`).
 * The :mod:`inspect` and :mod:`pydoc` modules are now capable of
-  correct introspection of a much wider variety of callable objects
+  correct introspection of a much wider variety of callable objects,
+  which improves the output of the Python :func:`help` system.
 * The :mod:`ipaddress` module API has been declared stable
 
 Security improvements:
@@ -161,11 +164,7 @@ CPython implementation improvements:
 * Leveraging :pep:`442`, :ref:`module globals are no longer set to None
   during finalization <whatsnew-pep-442>`, in most cases (:issue:`18214`).
 * :ref:`Configurable memory allocators <whatsnew-pep-445>` (:pep:`445`).
-* :ref:`Secure and interchangeable hash algorithm <whatsnew-pep-456>`
-  (:pep:`456`).
 * :ref:`Argument Clinic <whatsnew-pep-436>` (:pep:`436`).
-* The :mod:`marshal` format has been made :ref:`more compact and efficient
-  <whatsnew-marshal-3>` (:issue:`16475`).
 
 Please read on for a comprehensive list of user-facing changes, including many
 other smaller improvements, CPython optimizations, deprecations, and potential