Remove incorrect settlementAddress field from Payment test vector

Payment messages should not contain settlementAddress field per TAIP-14.
Only Authorize, Settle, and Revert messages should have settlementAddress.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: pelle

test-vectors/payment-request/valid-payto-invoice.json

@@ -22,10 +22,7 @@
         "name": "Merchant Services Inc",
         "account": "payto://ach/122000661/1234567890?receiver-name=Merchant%20Services%20Inc"
       },
-      "settlementAddress": "payto://ach/122000661/1234567890",
-      "fallbackSettlementAddresses": [
-        "payto://wire/122000661/1234567890"
-      ],
+      "fallbackSettlementAddresses": ["payto://wire/122000661/1234567890"],
       "agents": [
         {
           "@type": "Agent",
@@ -39,4 +36,4 @@
   "expectedResult": {
     "valid": true
   }
-}
+}