fix(vmtrace): return value pushed by smod

[banteg]

i was doing a pairwise comparison with geth trace and found a discrepancy in vmtrace. consider this request

trace_replayTransaction
['0x53546f6ac3d342842acfeeedeca5d66d7fda92acaa5bbc91ef94fd52b6f45a94', ['vmTrace']]

the stack divergest after this operation:

{
    "cost": 5,
    "ex": {
      "mem": null,
      "push": [],
      "store": null,
      "used": 298747
    },
    "pc": 17605,
    "sub": null,
    "op": "SMOD",
    "idx": "161-525-1253-663"
}

SMOD consumes two items from the stack and puts back one, but here it doesn't return what to push.

here is the same operation after the patch applied:

{
    "cost": 5,
    "ex": {
      "mem": null,
      "push": [
        "0x48"
      ],
      "store": null,
      "used": 298747
    },
    "pc": 17605,
    "sub": null,
    "op": "SMOD",
    "idx": "161-525-1253-663"
}