[3.13] gh-102809: No longer mention `Misc/gdbinit` in the code (GH-143980) (#144045)

gh-102809: No longer mention `Misc/gdbinit` in the code (GH-143980)

Fix misleading comment on `PyObject_Dump`.
(cherry picked from commit f84ea1107170988742fbd350123678a5c503c1ad)

Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>