chore: enable warnings as errors in docs build

noxfile.py

@@ -288,6 +288,7 @@ def docs(session):
     shutil.rmtree(os.path.join("docs", "_build"), ignore_errors=True)
     session.run(
         "sphinx-build",
+        "-W",  # warnings as errors
         "-T",  # show full traceback on exception
         "-N",  # no colors
         "-b",

owlbot.py

@@ -51,13 +51,6 @@
 
 python.py_samples(skip_readmes=True)
 
-# ignore docs warnings (only fail on errors). See b/275029141
-s.replace(
-    'noxfile.py',
-    '"-W",  # warnings as errors',
-    ''
-)
-
 # run format session for all directories which have a noxfile
 for noxfile in Path(".").glob("**/noxfile.py"):
     s.shell.run(["nox", "-s", "format"], cwd=noxfile.parent, hide_output=False)