Remove tomli from some build dependencies

[mkoeppe]

No longer needed because our current version of flit_core vendors it.

Also eliminates one use of --no-build-isolation.

📝 Checklist

• The title is concise, informative, and self-explanatory.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

[kwankyu]

flit_core installs tomli-w, instead of tomli. Is this only needed?

[mkoeppe]

flit_core installs tomli-w

I don't think it does; more info?

[kwankyu]

https://github.com/pypa/flit/blob/main/pyproject.toml ?

[kwankyu]

That's what https://pypi.org/project/flit-core/ leads me to.

[mkoeppe]

In that source tree, flit-core is found in the subdirectory https://github.com/pypa/flit/tree/main/flit_core; so https://github.com/pypa/flit/blob/main/flit_core/pyproject.toml is the relevant file.

[kwankyu]

Ah, thanks.

The relevant file has only dependencies = []. Then "flit_core vendors tomli"?

[mkoeppe]

flit_core vendors tomli

Yes, see https://github.com/pypa/flit/tree/main/flit_core/flit_core/vendor

[kwankyu]

I see. tomli is included. Thanks!

[kwankyu]

Sage builds well.

[mkoeppe]

Thanks!