fix: use absolute path to weight file for SigmaNet
The current path works when doing make test
because in that case the executable is started inside Rec/Phys/FunctorCore/tests/qmtest
.
But that's of course super fragile and when one launches the test manually e.g. by ./Rec/run gaudirun.py Rec/Phys/FunctorCore/tests/options/test_functors.py
the test will crash because it can not find the file.
cc @lecarus as original author.