statesync: keep peer despite lightblock query fail (#6692)

When a peer responds with no lightblock for the height we queried, we call the [removePeer method](https://github.com/tendermint/tendermint/blob/master/internal/statesync/reactor.go#L339). This removes the peer from the [dispatcher's list of called peer's](ad65883152/internal/statesync/dispatcher.go (L159)). When the dispatcher then receives responses from the removed peer, it [drops their responses](ad65883152/internal/statesync/dispatcher.go (L130)). These responses may be meaningful or contain a block or data that will help statesync proceed.

[The logs](https://gist.github.com/tychoish/34a1f61eaae3c36c23efc7d0001e805c), when this change is applied, show an additional 3 networking testnets passing. 

addresses:  #6691

internal/statesync/reactor.go

@@ -338,9 +338,6 @@ func (r *Reactor) backfill(
 					if lb == nil {
 						r.Logger.Info("backfill: peer didn't have block, fetching from another peer", "height", height)
 						queue.retry(height)
-						// as we are fetching blocks backwards, if this node doesn't have the block it likely doesn't
-						// have any prior ones, thus we remove it from the peer list
-						r.dispatcher.removePeer(peer)
 						continue
 					}