Update qml.matrix docs for wire ordering with qnodes

[mudit2812]

Context:
qml.matrix wire ordering with the new default.qubit was causing problems when device.wires=None. This is because when device.wires=None, the tape wires are used, the order of which is determined by which wires are used first, even with sequential integer wire labels.

Description of the Change:

• Added documentation to qml.matrix to provide more details on how the wire order is determined when using qml.matrix with a QNode.

Benefits:
Users may be less confused if qml.matrix gives a matrix with an unexpected wire order.

Possible Drawbacks:

Related GitHub Issues:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (370d9d4) 99.65% compared to head (d4e7983) 99.64%.
Report is 1 commits behind head on master.

Additional details and impacted files

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- Coverage   99.65%   99.64%   -0.02%     
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  Files         385      385              
  Lines       34719    34569     -150     
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- Hits        34599    34446     -153     
- Misses        120      123       +3     

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[mudit2812]

[sc-50654]

[trbromley]

Thanks @mudit2812! I like the addition of the note box to make things very clear. Can we also have it in the wire_order arg docstring?

        wire_order (Sequence[Any], optional): Order of the wires in the quantum circuit.
            The default wire order depends on the type of ``op``:

            - If ``op`` is a :class:`~.QNode`, then the wire order is determined by the
              associated device's wires, if provided.

            - Otherwise, the wire order is determined by the order in which wires
              appear in the circuit.

            - See the usage details for more information.

Feel free to reword some of the above!

[lillian542]

One formatting thing not rendering correctly, otherwise looks good to me! 🚀