Add an example of conflicting imports that doesn't exclusively use qualified names

In haskell/error-messages#100 I only did an example where both names are imported qualified, but I think the error would also be triggered by something like
```hs
module Greeting (W.greeting, greeting) where

import qualified World as W
import Universe (greeting)
```
and
```hs
module Greeting (W.greeting, module Universe) where

import qualified World as W
import Universe (greeting)
```
so doing at least one of those would probably be useful.