chore: temporary staging workaround

@Kha It seems the new builtin antiquotation notation you added depends
on the array literal notation that is not builtin. I got the following
error after `update-stage0`

```
Lean/PrettyPrinter/Delaborator/Builtins.lean:455:2: error: elaboration function for '_kind.term._@.Init.Data.Array.Basic._hyg.3391' has not been implemented
```

The base name changed from `_kind.term` to `termKind`. I had to change
it because every parser we were defining was in the artificial (sub-)namespace
`_kind` :)
We didn't notive because we didn't have scoped parsers.

src/Lean/PrettyPrinter/Delaborator/Builtins.lean

@@ -452,7 +452,7 @@ def delabStructureInstance : Delab := whenPPOption getPPStructureInstances do
       -- index 2 is unused.
       pure <| some (← descend ty 2 delab)
     else pure <| none
-  `({ $[$fields, ]* $lastField $[: $ty]? })
+  `(FIXME) -- `({ $[$fields, ]* $lastField $[: $ty]? })
 
 @[builtinDelab app.Prod.mk]
 def delabTuple : Delab := whenPPOption getPPNotation do