Apply suggestions from code review

Co-authored-by: Zachary Ware <zachary.ware@gmail.com>

Author: skirpichev

.github/workflows/posix-deps-apt.sh

@@ -1,8 +1,4 @@
 #!/bin/sh
-
-# Workaround missing on ubuntu 24.04 libmpdec-dev
-sudo add-apt-repository ppa:ondrej/php
-
 apt-get update
 
 apt-get -yq --no-install-recommends install \

Doc/whatsnew/3.16.rst

@@ -160,7 +160,7 @@ Deprecated C APIs
 Removed C APIs
 --------------
 
-* Remove the bundled libmpdec_ decimal library from the CPython source tree,
+* Remove the bundled copy of the libmpdec_ decimal library from the CPython source tree
   to simplify maintenence and updates. The :mod:`decimal` module will now
   unconditionally use the system's libmpdec decimal library. Also remove the
   now unused :option:`!--with-system-libmpdec` :program:`configure` flag.