[3.11] gh-110088: Fix asyncio test_prompt_cancellation() (GH-110157) (#110159)

gh-110088: Fix asyncio test_prompt_cancellation() (GH-110157)

Don't measure the CI performance: don't test the maximum elapsed
time. The check failed on a slow CI.
(cherry picked from commit c62b49ecc8da13fa9522865ef6fe0aec194fd0d8)

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