pl-device-test fix: do not differentiate Projector with respect to state

[vincentmr]

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---

Context:

Description of the Change:
Use vanilla NumPy arrays in test_projector_expectation to avoid differentiating qml.Projector with respect to the state attribute.

Benefits:

Possible Drawbacks:

Related GitHub Issues:

[trbromley]

Thanks @vincentmr! Which Shortcut story does this correspond to?

So the objective here is to get things compatible with lightning.kokkos? I'm just worried in case there is a test regression for other devices.

[vincentmr]

[sc-63107]

[vincentmr]

Thanks @vincentmr! Which Shortcut story does this correspond to?

So the objective here is to get things compatible with lightning.kokkos? I'm just worried in case there is a test regression for other devices.

We do not differentiate Projector w.r.t. state in the tests, but lightning.kokkos and (likely) lightning.gpu are trying to differentiate it since the parameter is pennylane.numpy. This is to restore compatibility with the Lightning devices.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.67%. Comparing base (9c9b6ba) to head (fc49d84).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5683      +/-   ##
==========================================
- Coverage   99.68%   99.67%   -0.01%     
==========================================
  Files         412      414       +2     
  Lines       38666    38522     -144     
==========================================
- Hits        38545    38398     -147     
- Misses        121      124       +3     

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[maliasadi]

Thanks @vincentmr!

[vincentmr]

[sc-63451]