Quickfix for copy and paste bug in futures.ipynb comments

Describe the issue: In the futures.ipynb there is an example with x, y, z variables, where in line 207 and 208 the comments for the assignments of y and z are indicating that the "inc" function is used, but instead "double" and "add" are used.

Minimal Complete Verifiable Example:

  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "%%time\n",
    "\n",
    "for i in range(256):\n",
    "    x = client.submit(inc, i)     # x = inc(i)\n",
    "    y = client.submit(double, x)  # y = inc(x)\n",
    "    z = client.submit(add, x, y)  # z = inc(y)\n",
    "    zs.append(z)"
   ]
  }

should be

 {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "%%time\n",
    "\n",
    "for i in range(256):\n",
    "    x = client.submit(inc, i)     # x = inc(i)\n",
    "    y = client.submit(double, x)  # y = double(x)\n",
    "    z = client.submit(add, x, y)  # z = add(x, y)\n",
    "    zs.append(z)"
   ]
  }

Anything else we need to know?: no, this is really a quick fix

Environment: Line 207 Line 208