Fix deprecation warning in re.sub for Python 3.13

[stinodego]

I know xlsx2csv doesn't officially support Python 3.13, but there is no reason it couldn't!

We support xlsx2csv as an engine in Polars and we'd like to support Python 3.13. Currently, using xlsx2csv works fine but it throws a deprecation warning: re.sub now expects the count parameter as a keyword argument rather than positional.

I checked earlier versions of Python (3.4 onwards and 2.7) and it seems that in all cases, the parameter is named count, so using a keyword argument here shouldn't break anything.

It was a simple fix, hopefully this can be a tiny step towards Python 3.13 support!

[dilshod]

let me know if you need a new version published

[stinodego]

let me know if you need a new version published

There's no real need for a new release - we'll add something in Polars to handle the warning for now. Just figured I'd contribute here since it was such an easy fix.