Remove deprecated CLI option --format

[MichaReiser]

Summary

Extracted from #9814

Removes the deprecated CLI option 'format' in favor of output-format. The option was deprecated in #8203

Test Plan

cargo run -p ruff -- --explain RET505 #  works
cargo run -p ruff -- --explain RET505 --output-format json # works
cargo run -p ruff -- --explain RET505 --format json # does not work anymore
error: unexpected argument '--format' found

  tip: to pass '--format' as a value, use '-- --format'

[MichaReiser]

Thanks @tibor-reiss

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.