Alpha/Delegation: do not activate delegate when crediting

Remove the unneeded method for a delegate to reactivate itself by
provisioning its account. The delegate should simply re-register as
delegate.

src/proto_alpha/lib_protocol/src/contract_storage.ml

@@ -488,20 +488,7 @@ let credit c contract amount =
   | Some balance ->
       Lwt.return Tez_repr.(amount +? balance) >>=? fun balance ->
       Storage.Contract.Balance.set c contract balance >>=? fun c ->
-      Roll_storage.Contract.add_amount c contract amount >>=? fun c ->
-      begin
-        match contract with
-        | Implicit delegate ->
-            Delegate_storage.registered c delegate >>= fun registered ->
-            if registered then
-              Roll_storage.Delegate.set_active c delegate >>=? fun c ->
-              return c
-            else
-              return c
-        | Originated _ ->
-            return c
-      end >>=? fun c ->
-      return c
+      Roll_storage.Contract.add_amount c contract amount
 
 let spend c contract amount =
   is_spendable c contract >>=? fun spendable ->