gh-41036: Remove tomli
tomli is a TOML parser that was needed for Python < 3.11. Since Python
3.11+, tomllib is part of the standard library. tomli-w (TOML writer) is
kept as it's still needed for writing TOML files.
Changes:
- Removed build/pkgs/tomli directory
- Updated package dependencies to remove tomli references
- Remove the unused 3.10 env file
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URL: https://github.com/sagemath/sage/pull/41036
Reported by: Chenxin Zhong
Reviewer(s): Copilot, Dima Pasechnik, Tobias Diez
