[3.13] Doc: C API: Move `tp_dealloc` paragraph to `tp_dealloc` section (GH-125737) (#125798)

It looks like commit 43cf44ddcce6b225f959ea2a53e4817244ca6054
(gh-31501) accidentally moved the paragraph to the `tp_finalize`
section when the intent was to move it to the `tp_dealloc` section
(according to the commit message).

(cherry picked from commit d880c83ff7fb2e464bc4f469d74cc3fc3eca082c)


Co-authored-by: Richard Hansen <rhansen@rhansen.org>