Revert Palik_LowLoss notebook updates

[marcorudolphflex]

Summary

• Reverts 5d443d38ea62824ab9b1c19a902881db97d6c379, "Update notebooks to use Palik_LowLoss (Update notebooks to use Palik_LowLoss #499)", for the affected notebooks.
• Leaves the custom_dictionary.json changes from the original commit in place.

Why

We mirror notebook changes directly to the public notebooks surface. The Palik_LowLoss change has not been included in a public Tidy3D release yet, so publishing these notebooks now can expose unreleased functionality to users.

The Palik_LowLoss notebook update should be re-applied after the next release that includes the corresponding Tidy3D change.

Validation

• git show --check --stat --oneline --no-renames HEAD
• Confirmed custom_dictionary.json is absent from the PR diff.

---

Note

Low Risk
Primarily updates example notebooks to reference Palik_Lossless materials instead of Palik_LowLoss, with minimal functional impact outside notebook simulation results.

Overview
Updates a large set of Jupyter notebooks to stop referencing unreleased Palik_LowLoss material-library entries and instead use Palik_Lossless for Si and/or SiO2 (including in a few MultiPhysicsMedium optical definitions). Also adjusts related explanatory text in ChargeSolver.ipynb to reflect the new material name.

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[github-actions]

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