Relax device-spec observables validation

[sergei-mironov]

Context: Quantum device config now contains only native observables (it means, handled by C-API), while the device.observables may contain additional non-native observables supported by the device Python API.

Description of the Change: By this PR we relax the observables validation.

Benefits: Fix support toml schema 2 configs.

Possible Drawbacks:

Related GitHub Issues:

• Remove non-native observables from TOML files pennylane-lightning#659
• Update device toml specs to schema 2 pennylane-lightning#642

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[erick-xanadu]

Do you know if this interferes with lightning latest changes? I am thinking specifically about the migration to the new device API.

[sergei-mironov]

Do you know if this interferes with lightning latest changes? I am thinking specifically about the migration to the new device API.

I don't know for sure, I think that it does not. It is only related to how we interpret the information contained in the toml files.

[erick-xanadu]

I don't know for sure, I think that it does not. It is only related to how we interpret the information contained in the toml files.

Thanks Sergei! I ran the latest/latest action on this branch and it is no different than main/latest/latest. I agree that this might be independent of the new device API.