test: Use int.to_bytes over struct packing

This is done in prepration for the scripted diff, which can not deal
with those lines.

test/functional/p2p_invalid_messages.py

@@ -5,7 +5,6 @@
 """Test node responses to invalid network messages."""
 
 import random
-import struct
 import time
 
 from test_framework.messages import (
@@ -233,7 +232,7 @@ class InvalidMessagesTest(BitcoinTestFramework):
                 '208d'))     # port
 
     def test_addrv2_unrecognized_network(self):
-        now_hex = struct.pack('<I', int(time.time())).hex()
+        now_hex = int(time.time()).to_bytes(4, "little").hex()
         self.test_addrv2('unrecognized network',
             [
                 'received: addrv2 (25 bytes)',