[3.13] pythongh-141004: Document PyDict_GET_SIZE (pythonGH-141078) (pythonGH-141083)

pythongh-141004: Document `PyDict_GET_SIZE` (pythonGH-141078)
(cherry picked from commit f0ab07f)

Co-authored-by: Peter Bierma <[email protected]>

Author: miss-islington

Doc/c-api/dict.rst

@@ -245,6 +245,11 @@ Dictionary Objects
    ``len(p)`` on a dictionary.
 
 
+.. c:function:: Py_ssize_t PyDict_GET_SIZE(PyObject *p)
+
+   Similar to :c:func:`PyDict_Size`, but without error checking.
+
+
 .. c:function:: int PyDict_Next(PyObject *p, Py_ssize_t *ppos, PyObject **pkey, PyObject **pvalue)
 
    Iterate over all key-value pairs in the dictionary *p*.  The