Update read_from_hdf5.py

Decode byte str to str.

pypesto/store/read_from_hdf5.py

@@ -144,6 +144,7 @@ def read(self, objective: ObjectiveBase = None) -> Problem:
         problem.x_fixed_vals = [float(val) for val in problem.x_fixed_vals]
         problem.x_fixed_indices = [int(ix) for ix in problem.x_fixed_indices]
         problem.x_names = [name.decode() for name in problem.x_names]
+        problem.x_scales = [scale.decode() for scale in problem.x_scales]
 
         return problem