docker: Fix python binary
docker: Fix python binary

Filebin unconditionally expects a 'python' command to be in path that is
compatible with the installed pygments library. For alpine, this means a
python3 binary. Therefore, we symlink /usr/bin/python3 to
/usr/bin/python.

Bluewind/filebin,Bluewind/filebin,Bluewind/filebin,Bluewind/filebin,Bluewind/filebin