docs: Clarify docs for error case of PyDict_GetItemRef (GH-149506)

(cherry picked from commit 3565d31)

Co-authored-by: Nathan Goldbaum <nathan.goldbaum@gmail.com>

Author: ngoldbaum

Doc/c-api/dict.rst

@@ -133,7 +133,7 @@ Dictionary Objects
    * If the key is present, set *\*result* to a new :term:`strong reference`
      to the value and return ``1``.
    * If the key is missing, set *\*result* to ``NULL`` and return ``0``.
-   * On error, raise an exception and return ``-1``.
+   * On error, raise an exception, set *\*result* to ``NULL`` and return ``-1``.
 
    .. note::