made imaginary-time evolution assert Hermiticity

since it really only counts as imaginary-time evolution if the Hamiltonian is Hermitian - otherwise it's just sparkling non-unitary propagator Trotterisation

Author: TysonRayJones

quest/src/api/trotterisation.cpp

@@ -207,6 +207,7 @@ void applyTrotterizedImaginaryTimeEvolution(Qureg qureg, PauliStrSum hamil, qrea
     validate_quregFields(qureg, __func__);
     validate_pauliStrSumFields(hamil, __func__);
     validate_pauliStrSumTargets(hamil, qureg, __func__);
+    validate_pauliStrSumIsHermitian(hamil, __func__);
     validate_trotterParams(qureg, order, reps, __func__);
 
     // exp(-tau H) = exp(x i H) | x=tau*i