TST(string dtype): Resolve xfails in stack_unstack (#60703)

Author: rhshadrach

pandas/tests/frame/test_stack_unstack.py

@@ -5,8 +5,6 @@
 import numpy as np
 import pytest
 
-from pandas._config import using_string_dtype
-
 from pandas._libs import lib
 
 import pandas as pd
@@ -1675,7 +1673,6 @@ def test_unstack_multiple_no_empty_columns(self):
         expected = unstacked.dropna(axis=1, how="all")
         tm.assert_frame_equal(unstacked, expected)
 
-    @pytest.mark.xfail(using_string_dtype(), reason="TODO(infer_string)", strict=False)
     @pytest.mark.filterwarnings(
         "ignore:The previous implementation of stack is deprecated"
     )
@@ -1923,7 +1920,6 @@ def test_stack_level_name(self, multiindex_dataframe_random_data, future_stack):
         expected = frame.stack(future_stack=future_stack)
         tm.assert_series_equal(result, expected)
 
-    @pytest.mark.xfail(using_string_dtype(), reason="TODO(infer_string)", strict=False)
     @pytest.mark.filterwarnings(
         "ignore:The previous implementation of stack is deprecated"
     )