scx_utils: fix clippy error.

[devnexen]

error: you are deriving `Hash` but have implemented `PartialEq` explicitly
   --> rust/scx_utils/src/energy_model.rs:27:28
    |
 27 | #[derive(Debug, Clone, Eq, Hash, Ord, PartialOrd)]

[JakeHillion]

Why is this the correct fix over deriving PartialEq? It seems to make the code more complex and more likely to get out of sync.

[devnexen]

It s not a required fix but I thought you would prefer to keep the PartialEq implementation (which seems to be just the same as the default behavior anyway).