Remove async_get_device_class_lookup from entity_registry (#114212)

This function was only ever used in homekit, and since there is
now an index of devices in the entity registry, homekit no longer
uses it.

I searched github code for all references to async_get_device_class_lookup
and the only think I could find using it were forks of core. It seems
unlikely that any custom components are affected by removing this
function

homeassistant/helpers/entity_registry.py

@@ -643,29 +643,6 @@ class EntityRegistry(BaseRegistry):
             run_immediately=True,
         )
 
-    @callback
-    def async_get_device_class_lookup(
-        self, domain_device_classes: set[tuple[str, str | None]]
-    ) -> dict[str, dict[tuple[str, str | None], str]]:
-        """Return a lookup of entity ids for devices which have matching entities.
-
-        Entities must match a set of (domain, device_class) tuples.
-        The result is indexed by device_id, then by the matching (domain, device_class)
-        """
-        lookup: dict[str, dict[tuple[str, str | None], str]] = {}
-        for entity in self.entities.values():
-            if not entity.device_id:
-                continue
-            device_class = entity.device_class or entity.original_device_class
-            domain_device_class = (entity.domain, device_class)
-            if domain_device_class not in domain_device_classes:
-                continue
-            if entity.device_id not in lookup:
-                lookup[entity.device_id] = {domain_device_class: entity.entity_id}
-            else:
-                lookup[entity.device_id][domain_device_class] = entity.entity_id
-        return lookup
-
     @callback
     def async_is_registered(self, entity_id: str) -> bool:
         """Check if an entity_id is currently registered."""