fix: remove local provider check

It doesn't actually work. Blocks are stored under /blocks and have been since
2015.

Furthermore, this is just wrong. We shouldn't go digging through the datastore
to see if we happen to have the block. If we want something like this, we should
include a blockstore in the provider manager.

Author: Stebalien

handlers.go

@@ -316,20 +316,8 @@ func (dht *IpfsDHT) handleGetProviders(ctx context.Context, p peer.ID, pmes *pb.
 
 	resp := pb.NewMessage(pmes.GetType(), pmes.GetKey(), pmes.GetClusterLevel())
 
-	// check if we have this value, to add ourselves as provider.
-	has, err := dht.datastore.Has(convertToDsKey(key))
-	if err != nil && err != ds.ErrNotFound {
-		// FIXME: This doesn't work reliably. If we want this check, we
-		// need a _blockstore_.
-		logger.Errorw("error checking datastore for block", "key", key, "error", err)
-		has = false
-	}
-
 	// setup providers
 	providers := dht.ProviderManager.GetProviders(ctx, key)
-	if has {
-		providers = append(providers, dht.self)
-	}
 
 	if len(providers) > 0 {
 		// TODO: pstore.PeerInfos should move to core (=> peerstore.AddrInfos).