Fix Polkadot node that points to the wrong chain

Polkadot's only node besides Gem's own was polkadot-relay-rest-api.parity.io, which serves the relay chain, while Gem keeps DOT on Asset Hub. Picked in Networks, it showed the relay balance (969.66 DOT against 765,615 DOT on Asset Hub for the same address) and built transfers for the relay chain with Asset Hub's Balances pallet index. Adding that URL as a custom node already fails with Invalid Network ID; the built-in list skipped that check. No public Asset Hub sidecar serves the /v1 routes, so the list is empty like Cardano's.

Author: gemdev111

core/crates/primitives/src/node_config.rs

@@ -150,7 +150,7 @@ pub fn get_nodes_for_chain(chain: Chain) -> Vec<Node> {
         Chain::Stellar => vec![Node::new("https://horizon.stellar.org", NodePriority::High)],
         Chain::Sonic => vec![Node::new("https://rpc.soniclabs.com", NodePriority::High)],
         Chain::Algorand => vec![Node::new("https://mainnet-api.algonode.cloud", NodePriority::High)],
-        Chain::Polkadot => vec![Node::new("https://polkadot-relay-rest-api.parity.io", NodePriority::High)],
+        Chain::Polkadot => vec![],
         Chain::Plasma => vec![Node::new("https://rpc.plasma.to", NodePriority::High)],
         Chain::Cardano => vec![],
         Chain::Abstract => vec![Node::new("https://api.mainnet.abs.xyz", NodePriority::High)],