Prepare UnboundP as VarP once more

- This was a mistaken attempt to fix the default case in some
  situations, but it has been fixed in other ways now, and interacts
  inappropriately with some other pattern compilation code.

parser-typechecker/src/Unison/Runtime/Pattern.hs

@@ -240,7 +240,7 @@ prepareAs (SequenceOpP _ p op q) u = do
 prepareAs p u = pure $ u <$ p
 
 preparePattern :: Var v => PatternP a -> PPM v (PatternV v)
-preparePattern (UnboundP _) = UnboundP <$> freshVar
+preparePattern (UnboundP _) = VarP <$> freshVar
 preparePattern (VarP _) = VarP <$> useVar
 preparePattern (AsP _ p) = prepareAs p =<< useVar
 preparePattern p = prepareAs p =<< freshVar