Drop unnecessary sync_wallets call in tests

As we now block `start()` on updating fees anyways we don't have to call
`sync_wallets` manually to check we're successfully connected to the
testnet esplora. We here remove this as it can be flaky dependent how
many requests the Esplora server is accepting and how often our CI runs
from the same machines...

Author: tnull

src/test/functional_tests.rs

@@ -324,7 +324,6 @@ fn connect_to_public_testnet_esplora() {
 	builder.set_esplora_server("https://blockstream.info/testnet/api".to_string());
 	let node = builder.build().unwrap();
 	node.start().unwrap();
-	node.sync_wallets().unwrap();
 	node.stop().unwrap();
 }