Improve doc comment of destructure_const

compiler/rustc_middle/src/query/mod.rs

@@ -978,7 +978,8 @@ rustc_queries! {
         desc { "converting type-level constant value to mir constant value"}
     }
 
-    /// Destructure a type-level constant ADT or array into its variant index and its field values.
+    /// Destructures array, ADT or tuple constants into the constants
+    /// of their fields.
     query destructure_const(key: ty::Const<'tcx>) -> ty::DestructuredConst<'tcx> {
         desc { "destructuring type level constant"}
     }