Fix "not a character boundary" panic in missing_copyright_notice

[MichaReiser]

The missing copyright notice only looks at the 1024 first bytes. However, this can go wrong for unicode text if the 1024 byte is not a character boundary (because it is a multibyte character).

ruff/crates/ruff/src/rules/flake8_copyright/rules/missing_copyright_notice.rs

Lines 36 to 40 in 2cf00fe

	let contents = if locator.len() < 1024 {
	locator.contents()
	} else {
	locator.up_to(TextSize::from(1024))
	};

Fix: Use is_char_boundary to find a valid char boundary close to 1024.

locator.contents().is_char_boundary(1024)

[WindowGenerator]

@MichaReiser Hello. Can I solve this bug?

[MichaReiser]

@WindowGenerator sure. #7012 or #7027 both contain a code snipped that triggers the error and you may want to use as a test case.

[qarmin]

This is fixed and can be closed