test: remove bare CTransaction .rehash()/.calc_sha256() calls

Since the previous commit, CTransaction object calls to the
methods `.rehash()` and `.calc_sha256()` are effectively no-ops
if the returned value is not used, so we can just remove them.

test/functional/interface_zmq.py

@@ -212,7 +212,6 @@ class ZMQTest (BitcoinTestFramework):
 
             # Should receive the coinbase raw transaction.
             tx = tx_from_hex(rawtx.receive().hex())
-            tx.calc_sha256()
             assert_equal(tx.hash, txid.hex())
 
             # Should receive the generated raw block.