test.nim: Cleaner example of usage

tests/test.nim

@@ -1,5 +1,5 @@
 import enso
-import std/strformat
+import std/[strformat, sugar]
 
 proc unsafe_void(str: string) =
   echo str
@@ -14,8 +14,8 @@ func main() =
   run strput("Hello from Enso!")
 
   let
-    out_void: IO[void] = lift do(): unsafe_void("void")
-    out_int:  IO[int]  = lift proc(): int = unsafe_int("int")
+    out_void: IO[void] = lift () => unsafe_void("void")
+    out_int:  IO[int]  = lift () => unsafe_int("int")
 
   out_void()
   run strput(fmt"{out_int()}")