Fix deprecated string[pyarrow_numpy] in test_to_numpy_pandas_string

Xref pandas-dev/pandas#60152

Author: weiji14

pygmt/tests/test_clib_to_numpy.py

@@ -371,7 +371,10 @@ def test_to_numpy_pandas_numeric_with_na(dtype, expected_dtype):
         "U10",
         "string[python]",
         pytest.param("string[pyarrow]", marks=skip_if_no(package="pyarrow")),
-        pytest.param("string[pyarrow_numpy]", marks=skip_if_no(package="pyarrow")),
+        pytest.param(
+            pd.StringDtype(storage="pyarrow", na_value=np.nan),
+            marks=skip_if_no(package="pyarrow"),
+        ),
     ],
 )
 def test_to_numpy_pandas_string(dtype):