### What it does
Checks for the creation of a `peekable` iterator that is never `.peek()`ed

### Why is this bad?
Creating a peekable iterator without using any of its methods is likely a mistake,
or just a leftover after a refactor.

### Example
```
let collection = vec![1, 2, 3];
let iter = collection.iter().peekable();

for item in iter {
    // ...
}
```

Use instead:
```
let collection = vec![1, 2, 3];
let iter = collection.iter();

for item in iter {
    // ...
}
```