Fix overdraft message (#500)

This PR fixes the currency that is mentioned in the overdraft message

src/models/overdraft.py

@@ -29,5 +29,5 @@ def eth(self) -> float:
     def __str__(self) -> str:
         return (
             f"Overdraft(solver={self.account} ({self.name}),"
-            f"period={self.period},owed={self.eth} ETH)"
+            f"period={self.period},owed={self.eth} native token units)"
         )