test: rename CTransaction .sha256 -> .txid_int for consistency

Note that we unfortunately can't use a scripted diff here, as the same
property name is also used for `CBlockHeader`/`CBlock` instances.

test/functional/feature_assumevalid.py

@@ -117,7 +117,7 @@ class AssumeValidTest(BitcoinTestFramework):
 
         # Create a transaction spending the coinbase output with an invalid (null) signature
         tx = CTransaction()
-        tx.vin.append(CTxIn(COutPoint(self.block1.vtx[0].sha256, 0), scriptSig=b""))
+        tx.vin.append(CTxIn(COutPoint(self.block1.vtx[0].txid_int, 0), scriptSig=b""))
         tx.vout.append(CTxOut(49 * 100000000, CScript([OP_TRUE])))
 
         block102 = create_block(self.tip, create_coinbase(height), self.block_time, txlist=[tx])