Remove $attr from QueryArenas/QueryCaches.

It doesn't make much sense to put the query doc comments on these
structs. (The doc comments *are* put on various query functions, where
it makes more sense.)

Author: nnethercote

compiler/rustc_middle/src/query/plumbing.rs

@@ -389,7 +389,6 @@ macro_rules! define_callbacks {
         #[derive(Default)]
         pub struct QueryArenas<'tcx> {
             $(
-                $(#[$attr])*
                 pub $name: if_arena_cache!(
                     [$($modifiers)*]
                     (TypedArena<<$V as $crate::query::arena_cached::ArenaCached<'tcx>>::Allocated>)
@@ -401,7 +400,7 @@ macro_rules! define_callbacks {
         #[derive(Default)]
         pub struct QueryCaches<'tcx> {
             $(
-                $(#[$attr])* pub $name: $name::Storage<'tcx>,
+                pub $name: $name::Storage<'tcx>,
             )*
         }