gh-144693: Clarify that PyFrame_GetBack does not raise exceptions (GH-144824)

(cherry picked from commit 8775f90)

Co-authored-by: Taegyun Kim <k.taegyun@gmail.com>
Co-authored-by: Sergey Miryanov <sergey.miryanov@gmail.com>
Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

Author: 3 people

Doc/c-api/frame.rst

@@ -50,6 +50,7 @@ See also :ref:`Reflection <reflection>`.
 
    Return a :term:`strong reference`, or ``NULL`` if *frame* has no outer
    frame.
+   This raises no exceptions.
 
    .. versionadded:: 3.9