jid: Fix a clippy warning

The other three are about missing Self in the new method’s return type,
but these return the Cow type instead so that’s how they’re meant to be.

jid/src/lib.rs

@@ -105,7 +105,7 @@ impl PartialEq for Jid {
 
 impl PartialOrd for Jid {
     fn partial_cmp(&self, other: &Jid) -> Option<Ordering> {
-        self.normalized.partial_cmp(&other.normalized)
+        Some(self.cmp(other))
     }
 }