Add link to relevant issue for unused variable preview behavior (#12841)

crates/ruff_linter/src/rules/pyflakes/rules/unused_variable.rs

@@ -261,6 +261,7 @@ pub(crate) fn unused_variable(checker: &Checker, scope: &Scope, diagnostics: &mu
             if (binding.kind.is_assignment()
                 || binding.kind.is_named_expr_assignment()
                 || binding.kind.is_with_item_var())
+                // Stabilization depends on resolving https://github.com/astral-sh/ruff/issues/8884
                 && (!binding.is_unpacked_assignment() || checker.settings.preview.is_enabled())
                 && binding.is_unused()
                 && !binding.is_nonlocal()