Switch quadratic interaction in diet example to ints

**Description**
[Diet Example](https://docs.ocean.dwavesys.com/en/stable/examples/hybrid_cqm_diet.html#variables) has this code:

```
>>> quantities[0] * quantities[1]
QuadraticModel({'rice': 0.0, 'tofu': 0.0}, {('tofu', 'rice'): 1.0}, 0.0,
{'rice': 'REAL', 'tofu': 'REAL'}, dtype='float64')
```

It should be switched to

```
>>> quantities[2] * quantities[5]
Out[7]: QuadraticModel({'banana': 0.0, 'avocado': 0.0}, {('avocado', 'banana'): 1.0}, 0.0, {'banana': 'INTEGER', 'avocado': 'INTEGER'}, dtype='float64')
```

**To Reproduce**
See above

**Expected behavior**
Need int vars, not real

**Environment:**
- OS: Any
- Python version: Any

**Additional context**
CC @tmittal7

And remove the ``# doctest: +SKIP`` that kept us from catching this earlier.