[refurb] Make list-reverse-copy an unsafe fix (#12303)

## Summary

I don't know that there's more to do here. We could consider not raising
the violation at all for arguments, but that would have some false
negatives and could also be surprising to users.

Closes #12267.

crates/ruff_linter/src/rules/refurb/rules/list_reverse_copy.rs

@@ -36,6 +36,14 @@ use crate::checkers::ast::Checker;
 /// l.reverse()
 /// ```
 ///
+/// ## Fix safety
+/// This rule's fix is marked as unsafe, as calling `.reverse()` on a list
+/// will mutate the list in-place, unlike `reversed`, which creates a new list
+/// and leaves the original list unchanged.
+///
+/// If the list is referenced elsewhere, this could lead to unexpected
+/// behavior.
+///
 /// ## References
 /// - [Python documentation: More on Lists](https://docs.python.org/3/tutorial/datastructures.html#more-on-lists)
 #[violation]
@@ -88,7 +96,7 @@ pub(crate) fn list_assign_reversed(checker: &mut Checker, assign: &StmtAssign) {
             },
             assign.range(),
         )
-        .with_fix(Fix::safe_edit(Edit::range_replacement(
+        .with_fix(Fix::unsafe_edit(Edit::range_replacement(
             format!("{}.reverse()", target_expr.id),
             assign.range(),
         ))),

crates/ruff_linter/src/rules/refurb/snapshots/ruff_linter__rules__refurb__tests__FURB187_FURB187.py.snap

@@ -10,7 +10,7 @@ FURB187.py:6:5: FURB187 [*] Use of assignment of `reversed` on list `l`
   |
   = help: Replace with `l.reverse()`
 
-ℹ Safe fix
+ℹ Unsafe fix
 3 3 | 
 4 4 | def a():
 5 5 |     l = []
@@ -29,7 +29,7 @@ FURB187.py:11:5: FURB187 [*] Use of assignment of `reversed` on list `l`
    |
    = help: Replace with `l.reverse()`
 
-ℹ Safe fix
+ℹ Unsafe fix
 8  8  | 
 9  9  | def b():
 10 10 |     l = []
@@ -48,7 +48,7 @@ FURB187.py:16:5: FURB187 [*] Use of assignment of `reversed` on list `l`
    |
    = help: Replace with `l.reverse()`
 
-ℹ Safe fix
+ℹ Unsafe fix
 13 13 | 
 14 14 | def c():
 15 15 |     l = []