Remove deprecated code from io.py (#203)

Remove the use of `pandas.save()` ([deprecated since pandas
1.5](https://pandas.pydata.org/pandas-docs/version/1.5.0/reference/api/pandas.ExcelWriter.save.html)).
`pandas.close()` is now sufficient to [save and close a
file](https://pandas.pydata.org/docs/dev/reference/api/pandas.ExcelWriter.close.html#pandas.ExcelWriter.close).
I have also updated the `setup.cfg` to require pandas 2.0.2 (the latest
release at the time of the PR).

setup.cfg

@@ -52,7 +52,7 @@ install_requires =
     networkx>=2.7
     numba>=0.53
     numpy>=1.21
-    pandas>=1.3
+    pandas>=2.0.2
     openpyxl>=2.6
     scikit-image>=0.17.1
     scipy>=1.7

src/skan/io.py

@@ -24,5 +24,4 @@ def write_excel(filename, **kwargs):
             obj = _params_dict_to_dataframe(obj)
         if isinstance(obj, pd.DataFrame):
             obj.to_excel(writer, sheet_name=sheet_name)
-    writer.save()
     writer.close()