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/feature_coinstatsindex.py

@@ -191,7 +191,6 @@ class CoinStatsIndexTest(BitcoinTestFramework):
         # has two outputs
         cb = create_coinbase(109, nValue=35)
         cb.vout.append(CTxOut(5 * COIN, CScript([OP_FALSE])))
-        cb.rehash()
 
         # Generate a block that includes previous coinbase
         tip = self.nodes[0].getbestblockhash()