Summary
--
This PR updates the docs for PLW1641 to place less emphasis on the
example of inheriting a parent class's `__hash__` implementation by both
reducing the length of the example and warning that it may be unsound in
general, as @AlexWaygood pointed out on Notion.
Test plan
--
Existing tests
---------
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
6cd0669475