move deprecation notice under the C API section instead

Author: picnixz

Doc/whatsnew/3.15.rst

@@ -1310,18 +1310,6 @@ Deprecated
 New deprecations
 ----------------
 
-* Build:
-
-  * Deprecate :pep:`456` support for providing an external definition
-    of the string hashing scheme. Removal is scheduled for Python 3.19.
-
-    Previously, embedders could define :c:macro:`Py_HASH_ALGORITHM` to be
-    ``Py_HASH_EXTERNAL`` to indicate that the hashing scheme was provided
-    externally but this feature was undocumented, untested and most likely
-    unused.
-
-    (Contributed by Bénédikt Tran in :gh:`141226`.)
-
 * :mod:`base64`:
 
   * Accepting the ``+`` and ``/`` characters with an alternative alphabet in
@@ -1550,6 +1538,16 @@ on Python 3.13 and older.
 Deprecated C APIs
 -----------------
 
+* Deprecate :pep:`456` support for providing an external definition
+  of the string hashing scheme. Removal is scheduled for Python 3.19.
+
+  Previously, embedders could define :c:macro:`Py_HASH_ALGORITHM` to be
+  ``Py_HASH_EXTERNAL`` to indicate that the hashing scheme was provided
+  externally but this feature was undocumented, untested and most likely
+  unused.
+
+  (Contributed by Bénédikt Tran in :gh:`141226`.)
+
 * For unsigned integer formats in :c:func:`PyArg_ParseTuple`,
   accepting Python integers with value that is larger than the maximal value
   for the C type or less than the minimal value for the corresponding