The httpx package emits some warnings when we run the tests in
`test_proxy_server.py`:
```shell
$ env -i PATH=$PATH poetry run pytest litellm/tests/test_proxy_server.py
...
litellm/tests/test_proxy_server.py::test_bedrock_embedding
litellm/tests/test_proxy_server.py::test_chat_completion
litellm/tests/test_proxy_server.py::test_chat_completion_azure
litellm/tests/test_proxy_server.py::test_chat_completion_optional_params
litellm/tests/test_proxy_server.py::test_embedding
litellm/tests/test_proxy_server.py::test_engines_model_chat_completions
litellm/tests/test_proxy_server.py::test_health
litellm/tests/test_proxy_server.py::test_img_gen
litellm/tests/test_proxy_server.py::test_openai_deployments_model_chat_completions_azure
.../site-packages/httpx/_client.py:680:
DeprecationWarning: The 'app' shortcut is now deprecated.
Use the explicit style 'transport=WSGITransport(app=...)' instead.
warnings.warn(message, DeprecationWarning)
...
```
Fixing this requires updating starlette, but the version of FastAPI in use
prevents that. So I updated FastAPI to update starlette to fix the httpx
warnings.
When run in combination with the changes in GH-3600, the tests pass and only
emit 1 warning!
```shell
$ env -i PATH=$PATH poetry run pytest litellm/tests/test_proxy_server.py
====================================== test session starts ======================================
platform darwin -- Python 3.12.3, pytest-7.4.4, pluggy-1.5.0
rootdir: /Users/abramowi/Code/OpenSource/litellm
plugins: anyio-4.3.0, mock-3.14.0
collected 12 items
litellm/tests/test_proxy_server.py s..........s [100%]
======================================= warnings summary ========================================
litellm/utils.py:43
/Users/abramowi/Code/OpenSource/litellm/litellm/utils.py:43: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
import pkg_resources # type: ignore
-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
=========================== 10 passed, 2 skipped, 1 warning in 8.81s ============================
```
