chore: update tests to be compatible with pandas 2.0 (#1538)

* chore: update tests to be compatible with pandas 2.0

* use StringDtype without storage argument

* avoid Float64Dtype on older pandas

tests/unit/test_table.py

@@ -3486,15 +3486,22 @@ def test_to_dataframe_w_dtypes_mapper(self):
             create_bqstorage_client=False,
             bool_dtype=pandas.BooleanDtype(),
             int_dtype=pandas.Int32Dtype(),
-            float_dtype=pandas.StringDtype(),
+            float_dtype=(
+                pandas.Float64Dtype()
+                if hasattr(pandas, "Float64Dtype")
+                else pandas.StringDtype()
+            ),
             string_dtype=pandas.StringDtype(),
         )
 
         self.assertIsInstance(df, pandas.DataFrame)
         self.assertEqual(df.complete.dtype.name, "boolean")
         self.assertEqual(df.age.dtype.name, "Int32")
         self.assertEqual(df.seconds.dtype.name, "Int32")
-        self.assertEqual(df.miles.dtype.name, "string")
+        self.assertEqual(
+            df.miles.dtype.name,
+            "Float64" if hasattr(pandas, "Float64Dtype") else "string",
+        )
         self.assertEqual(df.name.dtype.name, "string")
 
     @unittest.skipIf(pandas is None, "Requires `pandas`")