Pin Sphinx version (#1348)

Summary:
Pull Request resolved: #1348

`publish-stable-website` started failing when sphinx updated to version 6.0. See https://github.com/facebook/Ax/actions/runs/3801386293/jobs/6466164713.

Pinning sphinx to the version from this successful run to temporarily fix things: https://github.com/facebook/Ax/actions/runs/3798434044/jobs/6460138289

Reviewed By: saitcakmak

Differential Revision: D42281200

fbshipit-source-id: 2082ba143abab23012cf69d6d4cd600daec32f83

setup.py

@@ -41,8 +41,8 @@
     "Jinja2",
     "pytest>=4.6",
     "pytest-cov",
-    "sphinx",
-    "sphinx-autodoc-typehints",
+    "sphinx==5.3.0",
+    "sphinx-autodoc-typehints==1.19.5",
     "torchvision>=0.5.0",
     "nbconvert",
     "jupyter-client==6.1.12",