test: refactor: take use of create_block version parameter (or use default)

test/functional/feature_assumevalid.py

@@ -135,7 +135,6 @@ class AssumeValidTest(BitcoinTestFramework):
         # Bury the assumed valid block 2100 deep
         for _ in range(2100):
             block = create_block(self.tip, create_coinbase(height), self.block_time)
-            block.nVersion = 4
             block.solve()
             self.blocks.append(block)
             self.tip = block.sha256