CLN: err.orig in DataFrame.to_sql seems redundant
When going through the `DataFrame.sql` code in version `1.1.2` I found a part of the code confusing and seems redundant:

```python
except exc.SQLAlchemyError as err:
	# GH34431
	msg = "(1054, \"Unknown column 'inf' in 'field list'\")"
	err_text = str(err.orig)
	if re.search(msg, err_text):
		raise ValueError("inf cannot be used with MySQL") from err
	else:
		raise err
```

This is in pandas.io.sql line 1400-1407.


`err.orig` part seems wrong, and does not exist as a method in the sqlalchemy class `SQLAlchemyError`.

Should I remove it or am I missing something?