chore: remove pinned Sphinx version [autoapprove] (#640)

Source-Link: googleapis/synthtool@909573c
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:ddf4551385d566771dc713090feb7b4c1164fb8a698fe52bbe7670b24236565b

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:240b5bcc2bafd450912d2da2be15e62bc6de2cf839823ae4bf94d4f392b451dc
-# created: 2023-06-03T21:25:37.968717478Z
+  digest: sha256:ddf4551385d566771dc713090feb7b4c1164fb8a698fe52bbe7670b24236565b
+# created: 2023-06-27T13:04:21.96690344Z

noxfile.py

@@ -396,10 +396,9 @@ def docfx(session):
 
     session.install("-e", ".")
     session.install(
-        "sphinx==4.0.1",
+        "gcp-sphinx-docfx-yaml",
         "alabaster",
         "recommonmark",
-        "gcp-sphinx-docfx-yaml",
     )
 
     shutil.rmtree(os.path.join("docs", "_build"), ignore_errors=True)