Operator tutorials and opflow deprecation

[woodsp-ibm]

There are 2 tutorials in operators folder which relate to opflow content. One is about the opflow framework/function in general, the other is for gradients that are also part of opflow.

Opflow is soon to be deprecated - see #9176 so these tutorials should be addressed. We can at a minimum edit them to link to the opflow migration guide upfront along with suitable comments about the deprecation and alternate function. And potentially point to alternate tutorials:

• For operators I do not think I have seen a quantum_info tutorial around the operators there.

• For the gradients Update Gradient Framework tutorial to use primitives qiskit-tutorials#1390 this would be the 'replacement' tutorial using the gradient primitives from algorithms.

[javabster]

Update: moving forward we will keep the opflow tutorials until opflow itself is fully removed from Qiskit (v0.45), at which point we should also remove the opflow tutorials as well. To complete this issue we should add a note to the top of each opflow tutorial explaining the deprecation and when the module and tutorials will be removed

[woodsp-ibm]

I see #10682 adds a comment about the operator/opflow tutorials - maybe that suffices to address this issue.

[Eric-Arellano]

We will also want a note at the top of the operator tutorials themselves about the deprecation. I am working right now on migrating qiskit-tutorials into Qiskit. Once that copy is merged, I plan to add the note and then we can close this issue.

[Eric-Arellano]

This was fixed back when we had qiskit.org