pyextract: too many open files

[remytms]

When trying to use pyextract over a larger area I get the following errors:

$ python3 pyextract.py -g -i workingdir/in/osm/seamarks_planet.osm -o workingdir/ -y_min 150 -y_max 200 -x_min 230 -x_max 280
...
generate config file for command "osmium extract": workingdir/in/osm/seamarks_planet.osm
input file: workingdir/in/osm/seamarks_planet.osm
output dir: workingdir
x_min=230, x_max=280, y_min=150, y_max=200, z=9
2024-03-20 09:32:13,786 - pyextractr - INFO - generation failed outfile: outfile
2024-03-20 09:32:13,788 - pyextractr - ERROR - Open failed for 'workingdirosm-extracts/231-170-9.osm': Too many open files
...

I seams that we open too many file at once.

@stevo01 If you agree, I can be in charge of fixing that and making a pull request.