[ruff] add fix safety section (RUF017)

crates/ruff_linter/src/rules/ruff/rules/quadratic_list_summation.rs

@@ -46,6 +46,14 @@ use crate::importer::ImportRequest;
 /// functools.reduce(operator.iadd, lists, [])
 /// ```
 ///
+/// ## Fix safety
+///
+/// This fix is always marked as unsafe because `sum` uses the `__add__` magic method while
+/// `operator.iadd` uses the `__iadd__` magic method, and these behave differently on lists.
+/// The former requires the right summand to be a list, whereas the latter allows for any iterable.
+/// Therefore, the fix could inadvertently cause code that previously raised an error to silently
+/// succeed. Moreover, the fix could remove comments from the original code.
+///
 /// ## References
 /// - [_How Not to Flatten a List of Lists in Python_](https://mathieularose.com/how-not-to-flatten-a-list-of-lists-in-python)
 /// - [_How do I make a flat list out of a list of lists?_](https://stackoverflow.com/questions/952914/how-do-i-make-a-flat-list-out-of-a-list-of-lists/953097#953097)