Revert "Skip duplicated data when calculating fossil energy consumption (#60599)" (#61323)

This reverts commit 159506262a.

homeassistant/components/energy/websocket_api.py

@@ -274,16 +274,14 @@ async def ws_get_fossil_energy_consumption(
     ) -> dict[datetime, float]:
         """Combine multiple statistics, returns a dict indexed by start time."""
         result: defaultdict[datetime, float] = defaultdict(float)
-        seen: defaultdict[datetime, set[str]] = defaultdict(set)
 
         for statistics_id, stat in stats.items():
             if statistics_id not in statistic_ids:
                 continue
             for period in stat:
-                if period["sum"] is None or statistics_id in seen[period["start"]]:
+                if period["sum"] is None:
                     continue
                 result[period["start"]] += period["sum"]
-                seen[period["start"]].add(statistics_id)
 
         return {key: result[key] for key in sorted(result)}