Fix serve unit tests

Author: aviruthen

sagemaker-serve/src/sagemaker/serve/model_server/in_process_model_server/app.py

@@ -39,7 +39,6 @@ def __init__(
     ):
         self._thread = None
         self._loop = None
-        self._stop_event = asyncio.Event()
         self._shutdown_event = threading.Event()
         self._router = APIRouter()
         self._task = task

sagemaker-serve/tox.ini

@@ -87,8 +87,8 @@ allowlist_externals =
 commands =
     python -c "import os; os.system('install-custom-pkgs --install-boto-wheels')"
     pip install 'apache-airflow==2.10.4' --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-2.10.4/constraints-3.9.txt"
-    pip install 'torch==2.3.1+cpu' -f 'https://download.pytorch.org/whl/torch_stable.html'
-    pip install 'torchvision==0.18.1+cpu' -f 'https://download.pytorch.org/whl/torch_stable.html'
+    pip install 'torch==2.8.0' 'torchvision==0.21.0'
+    pip install 'onnx>=1.17.0' 'onnxruntime>=1.20.0'
     pip install 'dill>=0.3.9'
     pip install 'tensorflow==2.16.2'