Remove obsolete ConsensusEnsurer

As a result of #1657 out-of-place parent blocks are marked as non-consensus
more reliably, i.e. they will eventually be fetched even if first attempt is
unsuccessful.

The `ConsensusEnsurer` module, on the contrary, only tried refetching block
once, and left it as-is if the refetch failed. Now it is not needed anymore.

apps/indexer/lib/indexer/block/realtime/fetcher.ex

@@ -27,7 +27,7 @@ defmodule Indexer.Block.Realtime.Fetcher do
   alias Explorer.Chain.TokenTransfer
   alias Explorer.Counters.AverageBlockTime
   alias Indexer.{AddressExtraction, Block, TokenBalances, Tracer}
-  alias Indexer.Block.Realtime.{ConsensusEnsurer, TaskSupervisor}
+  alias Indexer.Block.Realtime.TaskSupervisor
   alias Timex.Duration
 
   @behaviour Block.Fetcher
@@ -269,12 +269,7 @@ defmodule Indexer.Block.Realtime.Fetcher do
   @decorate span(tracer: Tracer)
   defp do_fetch_and_import_block(block_number_to_fetch, block_fetcher, retry) do
     case fetch_and_import_range(block_fetcher, block_number_to_fetch..block_number_to_fetch) do
-      {:ok, %{inserted: inserted, errors: []}} ->
-        for block <- Map.get(inserted, :blocks, []) do
-          args = [block.parent_hash, block.number - 1, block_fetcher]
-          Task.Supervisor.start_child(TaskSupervisor, ConsensusEnsurer, :perform, args)
-        end
-
+      {:ok, %{inserted: _, errors: []}} ->
         Logger.debug("Fetched and imported.")
 
       {:ok, %{inserted: _, errors: [_ | _] = errors}} ->