[pyupgrade] Add fix safety section to docs (UP030) (#17443)

## Summary

add fix safety section to format_literals, for #15584

Author: Kalmaegi

crates/ruff_linter/src/rules/pyupgrade/rules/format_literals.rs

@@ -39,6 +39,10 @@ use crate::Locator;
 /// "{}, {}".format("Hello", "World")  # "Hello, World"
 /// ```
 ///
+/// This fix is marked as unsafe because:
+/// - Comments attached to arguments are not moved, which can cause comments to mismatch the actual arguments.
+/// - If arguments have side effects (e.g., print), reordering may change program behavior.
+///
 /// ## References
 /// - [Python documentation: Format String Syntax](https://docs.python.org/3/library/string.html#format-string-syntax)
 /// - [Python documentation: `str.format`](https://docs.python.org/3/library/stdtypes.html#str.format)