getiterator deprecated in Python 3.9; failure to call pd.read_excel()
I've read here https://stackoverflow.com/a/64744395 that `getiterator` has been deprecated in Python 3.9.0. My script ran without issues until upgrading Python to 3.9, and now I get the following error:

```python
Traceback (most recent call last):
  File "/Users/user/Documents/Programming/MyProject/MyProject.py", line 551, in <module>
    df = pd.read_excel(excel_filename, excel_sheetname)
    ...
AttributeError: 'ElementTree' object has no attribute 'getiterator'
```

Running Python 3.9.0, Pandas 1.1.4