lightningd/chaintopology.h: Remove unused `txnums` field from `struct block`.

Changelog-None internal cleanup

lightningd/chaintopology.c

@@ -840,7 +840,6 @@ static struct block *new_block(struct chain_topology *topo,
 
 	b->hdr = blk->hdr;
 
-	b->txnums = tal_arr(b, u32, 0);
 	b->full_txs = tal_steal(b, blk->tx);
 
 	return b;

lightningd/chaintopology.h

@@ -60,10 +60,7 @@ struct block {
 	/* Key for hash table */
 	struct bitcoin_blkid blkid;
 
-	/* And their associated index in the block */
-	u32 *txnums;
-
-	/* Full copy of txs (trimmed to txs list in connect_block) */
+	/* Full copy of txs (freed in filter_block_txs) */
 	struct bitcoin_tx **full_txs;
 };