Fix default value for multi_level_index in multi.py

[dhruvan2006]

Fix the default value for the multi_level_index parameter in the download function. Was changed from True to False to reflect expected behavior.

Resolves #2101

[ValueRaider]

~But True is still broken, it should still contain a DatetimeIndex.~

[dhruvan2006]

But isn't the index Date column still a DatetimeIndex?

[ValueRaider]

You're right. I was going purely off the screenshot showing integer index.