[3.12] Revert "gh-128364: Fix flaky `test_timeout` test (gh-130724)" (gh-130732) (#130735)

Revert "gh-128364: Fix flaky `test_timeout` test (gh-130724)" (gh-130732)

Change broke Android and iOS buildbots that do not have multiprocessing.

This reverts commit cfa0b1dc375e63cde28e61a47108c645b0e74834.
(cherry picked from commit 5221d9ce0e2beb0fe04bed072e1bb448fd522882)

Co-authored-by: Sam Gross <colesbury@gmail.com>