Tutorials should not use get_statevector

[yaelbh]

result.get_statevector belongs to the old Aer interface, where we had separate qasm and statevector simulators. With the move to Aer 0.8, the instruction save_statevector was correctly added to the tutorials, but the call to get_statevector is still there.

[MartinBeseda]

@yaelbh I could take a look at it, if the tutorials aren't fixed yet.

[yaelbh]

Ok, thanks. I'm not absolutely sure if the issue is correct. @chriseclectic or @mtreinish will probably know.

[Eric-Arellano]

The API still exists as of Qiskit 0.44. So this should be fine. https://qiskit.org/documentation/stubs/qiskit.result.Result.html#qiskit.result.Result.get_statevector