STAN-0302 is triggered on long contexts

The following code:

```
type Differentiable f =
( Functor f,
GenericK f,
GDifferentiable (RepK f),
GBifunctor (GDiff (RepK f))
)
```

triggers this message from stan in HLS:

```
✲ Name: Big tuples
✲ Description: Using tuples of big size (>= 4) can decrease code readability
✲ Severity: Style
✲ Category: #AntiPattern #Syntax
Possible solutions:
- Consider defining and using a custom data type to improve code comprehension
stan(STAN-0302)
```

However, this is not a tuple. It is a context, and there is no way to define a custom data type to improve code comprehension.

Start by reproducing STAN-0302 with the Differentiable context shown in the issue and inspect the rule's implementation and existing tests. Done means this context is no longer reported as a big tuple while actual large tuples continue to receive the intended diagnostic.

Written by the indexing model from the issue text.