fix(cli): correctly construct the TerminateSectors params

[beck-8]

I'm not sure if this will actually save gasused, but I think the theory will. If I'm wrong, please don't hesitate to close this PR.

before

{
  "Terminations": [
    {
      "Deadline": 2,
      "Partition": 0,
      "Sectors": "2500"
    },
    {
      "Deadline": 2,
      "Partition": 0,
      "Sectors": "2501"
    },]}

after

{
 "Terminations": [
   {
     "Deadline": 2,
     "Partition": 0,
     "Sectors": "2500-2501"
   },]}

[tediou5]

Look good to me, thank you very much.

[tediou5]

I'll run some tests to see if this approach actually saves on gas.

[eddieperez88]

Nice