unskip potentially flaky test on windows (#41000)

After PR #35526 the test_multiprocessing_client_mode test became flaky on windows. It was skipped in #35534. Let's see if it passes now

Signed-off-by: mattip <matti.picus@gmail.com>
Co-authored-by: Archit Kulkarni <architkulkarni@users.noreply.github.com>

ci/ci.sh

@@ -257,7 +257,6 @@ test_python() {
       -python/ray/tests:test_job
       -python/ray/tests:test_memstat
       -python/ray/tests:test_multi_node_3
-      -python/ray/tests:test_multiprocessing_client_mode # Flaky on Windows
       -python/ray/tests:test_object_manager # OOM on test_object_directory_basic
       -python/ray/tests:test_resource_demand_scheduler
       -python/ray/tests:test_stress  # timeout