[`pylint`] Clarify fix safety to include left-hand hashability (`PLR6201`) (#20518)

## Summary

Fixes #20510

crates/ruff_linter/src/rules/pylint/rules/literal_membership.rs

@@ -25,9 +25,11 @@ use crate::{AlwaysFixableViolation, Edit, Fix};
 ///
 /// ## Fix safety
 /// This rule's fix is marked as unsafe, as the use of a `set` literal will
-/// error at runtime if the sequence contains unhashable elements (like lists
-/// or dictionaries). While Ruff will attempt to infer the hashability of the
-/// elements, it may not always be able to do so.
+/// error at runtime if either the element being tested for membership (the
+/// left-hand side) or any element of the sequence (the right-hand side)
+/// is unhashable (like lists or dictionaries). While Ruff will attempt to
+/// infer the hashability of both sides and skip the fix when it can determine
+/// that either side is unhashable, it may not always be able to do so.
 ///
 /// ## References
 /// - [What’s New In Python 3.2](https://docs.python.org/3/whatsnew/3.2.html#optimizations)