Fix Krylov tutorial being Heron-specific

[Eric-Arellano]

Closes #3202. See #3217 for the original PR.

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One or more of the following people are relevant to this code:

• @miamico

[miamico]

maybe we should just leave out the min_num_qubits argument in the backend? The way it is written now (156q minimum) will not pick any backend if the user only has access to eagle devices (127q) or the ibm_torino qpu (133q), which is basically all the open plan users

[Eric-Arellano]

maybe we should just leave out the min_num_qubits argument in the backend?

Do you remember why it was changed in the first place? I was only copying your change. I'm happy to revert it back to 127.

I think @beckykd normally has us set the argument so that things like simulators aren't used, iirc? Or maybe it's a holdover from when we had smaller devices and isn't necessary anymore?

[miamico]

Oh I see. The 156 suggests an attempt to force the use of the latest heron devices but that actually cuts out open plan users so we should probably not do it. 127 would be good as it allows both eagles and older herons to be selected

[beckykd]

127 would be good

Isn't 127 the minimum that we have? We might as well just leave it off. And yes, I usually include an argument that ensures that a simulator isn't used: "simulator=False"

[miamico]

Looks good!