test: Use uninvolved pruned node in feature_pruning undo test

After fixing the nTime variable name, the test_pruneheight_undo_presence
test began failing because node 2, which is involved in reorg testing,
could be on a different chain than other nodes. This caused failures
when trying to fetch blocks from other nodes that didn't recognize
node 2's chain.

Switch to using node 5 instead, which is also a pruned node but isn't
involved in reorg testing, ensuring it stays on the same chain as the
other nodes. This allows the block fetching to work as intended in the
test.

test/functional/feature_pruning.py

@@ -500,11 +500,11 @@ class PruneTest(BitcoinTestFramework):
             "start", [{"desc": f"raw({false_positive_spk.hex()})"}], 0, 0, "basic", {"filter_false_positives": True})
 
     def test_pruneheight_undo_presence(self):
-        node = self.nodes[2]
+        node = self.nodes[5]
         pruneheight = node.getblockchaininfo()["pruneheight"]
         fetch_block = node.getblockhash(pruneheight - 1)
 
-        self.connect_nodes(1, 2)
+        self.connect_nodes(1, 5)
         peers = node.getpeerinfo()
         node.getblockfrompeer(fetch_block, peers[0]["id"])
         self.wait_until(lambda: not try_rpc(-1, "Block not available (pruned data)", node.getblock, fetch_block), timeout=5)