[fix] remove Fabric file

The fabfile.py has not been updated since 5 years.  I also asked [1] if someone
still use Fabric wtihout any response.  Lets drop outdated Fabric file.

[1] https://github.com/searx/searx/discussions/2400



Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>