Fix whatsnew reference.

Author: ZeroIntensity

Doc/whatsnew/3.15.rst

@@ -88,7 +88,6 @@ Summary -- Release highlights
 * :pep:`800`: Disjoint bases in the type system
 * :pep:`782`: :ref:`A new PyBytesWriter C API to create a Python bytes object
   <whatsnew315-pybyteswriter>`
-* :pep:`803`: :ref:`Stable ABI for Free-Threaded Builds <whatsnew315-abi3t>`
 * :pep:`803`, :pep:`820 <820>`, :pep:`793 <793>`:
   :ref:`Stable ABI for free-threaded builds <whatsnew315-abi3t>` and
   related C API