[3.12] gh-101100: Fix sphinx warnings in `c-api/file.rst` (GH-114546) (#114584)

* gh-101100: Fix sphinx warnings in `c-api/file.rst` (GH-114546)
(cherry picked from commit 01d970c1b8acf3ccf199d5de151a635ffd9d8c61)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>