Octopus Energy v12 breaks set schedule

[martinpelant]

They removed last_evaluated attribute from all entities which will cause this to always fail: https://github.com/gndean/home-assistant-hypervolt-charger/blob/main/custom_components/hypervolt_charger/service.py#L67

and needs to be replaced with something like target_times_last_evaluated (tested locally and seems to work)