[developers] python-3.13 is dropping future

Hi,

python-3.13 will drop "future". It seems most of the drivers which use it have conditional import, but tox still hard requires it. For support of the python-3.13 the tox "future" requirement will have to be dropped/relaxed. I tried to drop it in my fedora-41 python-3.13 test build and it seems it builds/tests OK

thanks & regards

Jaroslav