test: remove ToHex helper, use .serialize().hex() instead

test/functional/feature_pruning.py

@@ -11,8 +11,12 @@ This test takes 30 mins or more (up to 2 hours)
 import os
 
 from test_framework.blocktools import create_coinbase
-from test_framework.messages import CBlock, ToHex
-from test_framework.script import CScript, OP_RETURN, OP_NOP
+from test_framework.messages import CBlock
+from test_framework.script import (
+    CScript,
+    OP_NOP,
+    OP_RETURN,
+)
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -62,7 +66,7 @@ def mine_large_blocks(node, n):
         block.solve()
 
         # Submit to the node
-        node.submitblock(ToHex(block))
+        node.submitblock(block.serialize().hex())
 
         previousblockhash = block.sha256
         height += 1