Remove tab-size setting

[MichaReiser]

Summary

The tab-size setting was deprecated in Ruff 0.1.2 and using it is an error since Ruff 0.5 (#12006).

This PR removes the option entirely.

Closes #12041

Test Plan

ruff failed
  Cause: Failed to parse /home/micha/astral/test/pyproject.toml
  Cause: TOML parse error at line 1, column 1
  |
1 | [tool.ruff]
  | ^^^^^^^^^^^
unknown field `tab-size`

[AlexWaygood]

It's been deprecated for a very long time so I'm okay with removing it, but I also think it would be fine to leave the nice error message there for another minor version. It's not really a maintenance burden 😄

[codspeed-hq]

CodSpeed Performance Report

Merging #12835 will not alter performance

_{Comparing remove-tab-size-setting (233ce67) with ruff-0.7 (2a615d2)}

Summary

✅ 32 untouched benchmarks

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[MichaReiser]

It's been deprecated for a very long time so I'm okay with removing it, but I also think it would be fine to leave the nice error message there for another minor version. It's not really a maintenance burden 😄

I consider it a maintenance burden because we consider it for removal in every minor but never go through with it. That's why we should either decide to close the tasks and not remove them until 1.0 (or in ten years when the above argument no longer applies) or to go forward with it.

[AlexWaygood]

Thanks!