Fix bad key names in a couple of queries.

Due to a bug, you can currently use `key` within the `desc` block and
it'll just work regardless of what actual key name you specified. A
subsequent commit will fix this, so let's correct the affected queries
first.

compiler/rustc_middle/src/queries.rs

@@ -589,7 +589,7 @@
     }
 
     /// Checks whether a type is representable or infinitely sized
-    query representability(_: LocalDefId) -> rustc_middle::ty::Representability {
+    query representability(key: LocalDefId) -> rustc_middle::ty::Representability {
         desc { "checking if `{}` is representable", tcx.def_path_str(key) }
         // infinitely sized types will cause a cycle
         cycle_delay_bug
@@ -600,7 +600,7 @@
     }
 
     /// An implementation detail for the `representability` query
-    query representability_adt_ty(_: Ty<'tcx>) -> rustc_middle::ty::Representability {
+    query representability_adt_ty(key: Ty<'tcx>) -> rustc_middle::ty::Representability {
         desc { "checking if `{}` is representable", key }
         cycle_delay_bug
         anon