Remove allow-unused-imports setting from the common lint options

[MichaReiser]

Summary

Fixes #13668

Luckily, the lint.allow_unused_imports setting isn't read anywhere.
However, this could still be considered a breaking change because Ruff might fail to read a previously valid configuration.
I do think that it should be very unlikely, considering that the configuration was "useless" before.

The setting remains available under lint.pyflakes

ruff/crates/ruff_workspace/src/options.rs

Lines 2824 to 2829 in 0035ca9

	#[option(
	default = r#"[]"#,
	value_type = "list[str]",
	example = r#"allowed-unused-imports = ["hvplot.pandas"]"#
	)]
	pub allowed_unused_imports: Option<Vec<String>>,

Test Plan

cargo test

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[AlexWaygood]

LGTM as part of a minor release (which it will be!)