TST: update ruff and codespell versions

[hagenw]

Update ruff and codespell pre-commits to the versions we now use in other packages.

Summary by Sourcery

Add a utility function for managing environment variables and update pre-commit hooks to newer versions of ruff and codespell.

New Features:

• Add a utility function to set or delete environment variables.

Build:

• Update pre-commit configuration to use ruff version 0.7.0 and codespell version 2.3.0.

[sourcery-ai]

Reviewer's Guide by Sourcery

This PR updates the pre-commit configuration and adds a new utility function for environment variable management. The changes include upgrading ruff and codespell versions in the pre-commit configuration, and introducing a new helper function to handle environment variables.

No diagrams generated as the changes look simple and do not need a visual representation.

File-Level Changes

Change	Details	Files
Update pre-commit tool versions	Upgrade ruff-pre-commit from v0.1.8 to v0.7.0 Upgrade codespell from v2.2.4 to v2.3.0	.pre-commit-config.yaml
Add new utility function for environment variable management	Implement set_or_delete_env_variable function to handle setting or removing environment variables Add docstring with parameter descriptions	audeer/core/utils.py

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