PyPSA v1 deprecation warnings

[euronion]

Address some PyPSA v1 deprecation warnings.
The changes should be compatible with 0.33.2, at least according to the release notes.

Or was there a different plan for when/how to address the warnings?

Changes proposed in this Pull Request

Checklist

• I tested my contribution locally and it works as intended.
• Code and workflow changes are sufficiently documented.
• Changed dependencies are added to pixi.toml (using pixi add <dependency-name>).
• Changes in configuration options are added in config/config.default.yaml.
• Changes in configuration options are documented in doc/configtables/*.csv.
• Sources of newly added data are documented in doc/data_sources.rst.
• A release note doc/release_notes.rst is added.

[tgilon]

Thank you @euronion !

[euronion]

@lkstrp I think it would be really nice if we could create a recipe for semi-automatic migration between versions, e.g. using open-rewrite or similar. The changes necessary are not too complex in the model, but locating the relevant lines is tedious and can easily miss something.