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.

added Functors bug fix testing labels

/ci-test

added RTA label

added ci-test-triggered label

• [2022-02-14 14:16] Validation started with lhcb-master-mr#3700

resolved all threads

merged

mentioned in commit c2951393

mentioned in issue Moore#390 (closed)