gh-120635: Avoid leaking processes in test_pyrepl (#120676)

If the child process takes longer than SHORT_TIMEOUT seconds to
complete, kill the process but then wait until it completes with no
timeout to not leak child processes.

Lib/test/test_pyrepl/test_pyrepl.py

@@ -890,5 +890,5 @@ class TestMain(TestCase):
             exit_code = process.wait(timeout=SHORT_TIMEOUT)
         except subprocess.TimeoutExpired:
             process.kill()
-            exit_code = process.returncode
+            exit_code = process.wait()
         return "\n".join(output), exit_code