[hook] delete_doc is a staticmethod => remove `self` argument

cubicweb_elasticsearch/hooks.py

@@ -66,7 +66,7 @@
 class IndexEsOperation(hook.DataOperationMixIn, hook.Operation):
 
     @staticmethod
-    def delete_doc(self, es, **kwargs):
+    def delete_doc(es, **kwargs):
         try:
             # TODO option for async ?
             es.delete(**kwargs)