Fix force_download of files on Windows
On Windows, `os.rename` gives the error
```
FileExistsError: [WinError 183] Cannot create a file when that file already exists:
```
when trying to re-download a model that already exists in cache using `force_download=True`.
Can't test this right now as I don't have access to a Windows machine - does this still work if the model doesn't already exist?<|||||>> 
> 
> Can't test this right now as I don't have access to a Windows machine - does this still work if the model doesn't already exist?

Yes, I tested that 😄. There shouldn't be any further differences between `rename` and `replace`. Here's [what the documentation says](https://docs.python.org/3/library/os.html#os.replace).