[3.13] gh-121008: Fix idlelib.run tests (GH-121046) (#121049)

gh-121008: Fix idlelib.run tests (GH-121046)

When testing IDLE, don't create a Tk to avoid side effects such as
installing a PyOS_InputHook hook.
(cherry picked from commit 44eafd66882589d4f4eb569d70c49724da3e9291)

Co-authored-by: Victor Stinner <vstinner@python.org>