pytest: Fix up test_pay_no_secret to wait for node_announcements

This was racy since we didn't know whether the peer supports TLV payloads yet
so we defaulted to legacy, which doesn't support secrets.

tests/test_pay.py

@@ -2466,7 +2466,7 @@ def test_tlv_or_legacy(node_factory, bitcoind):
 @unittest.skipIf(not DEVELOPER, 'Needs dev-routes')
 @unittest.skipIf(TEST_NETWORK != 'regtest', "Invoice is network specific")
 def test_pay_no_secret(node_factory, bitcoind):
-    l1, l2 = node_factory.line_graph(2, wait_for_announce=False)
+    l1, l2 = node_factory.line_graph(2, wait_for_announce=True)
 
     l2.rpc.invoice(100000, "test_pay_no_secret", "test_pay_no_secret",
                    preimage='00' * 32, expiry=2000000000)