c tester (c/tester.js) was using a method to read the witness file
called 'readBinaryFile' that was obtaining a wrong number of witness
elements, and as consequence was returning a wrong array of witness.

Changed that method to 'readBinWitnessFile', which makes use of
wtnsUtils method from snarkjs to read the witness binary file, so now
the c tester returns the correct witness.