test: capture deprecation warning in repr_rows conflict case

DataFrameHtmlFormatter(repr_rows=..., max_rows=...) fires the deprecation
warning before raising ValueError, but pytest.raises does not catch warnings.
The escaping warning surfaced in every pytest run. Wrap the call in both
pytest.raises and pytest.warns so the warning is asserted, not leaked.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: timsaucer

python/tests/test_dataframe.py

@@ -1704,8 +1704,12 @@ def test_repr_rows_backward_compatibility(clean_formatter_state):
     assert formatter.max_rows == 15
     assert formatter.repr_rows == 15
 
-    # Should fail when conflicting with max_rows
-    with pytest.raises(ValueError, match="Cannot specify both repr_rows and max_rows"):
+    # Should fail when conflicting with max_rows. The deprecation warning still
+    # fires before the ValueError, so assert both.
+    with (
+        pytest.raises(ValueError, match="Cannot specify both repr_rows and max_rows"),
+        pytest.warns(DeprecationWarning, match="repr_rows parameter is deprecated"),
+    ):
         DataFrameHtmlFormatter(repr_rows=5, max_rows=10)
 
     # Setting repr_rows via property should warn