fix: replace _ with - when creating environments from features

[wolfv]

I had a pyproject.toml that was using optional deps like:

[project.optional-dependencies]
test = ["pytest"]
conda_build = ["bla"]

Upon conversion, pixi complained because

  × failed to parse project manifest
    ╭─[pyproject.toml:26:1]
 25 │ default = { solve-group = "default" }
 26 │ conda_build = { features = ["conda_build"], solve-group = "default" }
    · ─────┬─────
    ·      ╰── Failed to parse environment name 'conda_build', please use only lowercase letters, numbers and dashes
 27 │ test = { features = ["test"], solve-group = "default" }
    ╰────

This fixes that issue.

[ruben-arts]

thanks