Fix ES indexer didnt index on update

Author: Tschuppi81

Diff for: src/onegov/search/indexer.py

@@ -367,8 +367,7 @@ def delete(self, task: DeleteTask) -> None:
                     pass
 
     def update(self, task: IndexTask) -> None:
-        # not needed for elasticsearch
-        pass
+        self.index(task)
 
 
 class PostgresIndexer(IndexerBase):