test: skip ai/ml doctests (#17401)

Fixes #<521482448> 🦕

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: shuoweil

packages/bigframes/noxfile.py

@@ -428,6 +428,16 @@ def doctest(session: nox.sessions.Session):
             "bigframes/display/anywidget.py",
             "--ignore",
             "bigframes/bigquery/_operations/ai.py",
+            "--ignore",
+            "bigframes/bigquery/ai.py",
+            "--ignore",
+            "bigframes/ml",
+            "--ignore",
+            "bigframes/operations/ai.py",
+            "--ignore",
+            "bigframes/operations/semantics.py",
+            "--ignore",
+            "third_party/bigframes_vendored/sklearn",
         ),
         test_folder="bigframes",
         check_cov=True,