Remove eta expanded ability operation in docs

[pchiusano]

{{

```
Stream.toList! ’let foreach Stream.emit [“duck”, “rabbit”, “beaver”]
}}
```

This shows _eta -> Stream _eta in the rendered form of the example.

[runarorama]

This is still happening, and I think the reason is that this variable somehow becomes a User "_eta" instead of an Eta.

[pchiusano]

Idea for fix: just do eta reduction willy nilly during decompilation. While eta reduction isn't safe general for function with arbitrary effects, if the function just calls a data constructor (not an ability constructor), it's safe.

[pchiusano]

Implementation idea: more calls to etaReduceEtaVars in Decompile.hs. Maybe a "safe" version of eta reduce that only does it for data constructor calls.

[pchiusano]

Hit this again. It makes my otherwise lovely code...

... turn into this monstrosity :)

Gak!