Autocompletion snippet wrongly adds type when completing constructor

[lorenzo]

When completing form example the following:

let a = fromJust Not

And selecting Nothing from the list. You get a wrong snippet:

let a = fromJust Nothing Maybe a

We should omit the last placeholder when completing a constructor

[lorenzo]

Whoever wants to fix this issue, will need to modify this function:

• https://github.com/haskell/haskell-ide-engine/blob/master/src/Haskell/Ide/Engine/Plugin/HieExtras.hs#L103-L133

and also write a test case here:

https://github.com/haskell/haskell-ide-engine/blob/master/test/functional/CompletionSpec.hs