Remove $tcx metavariable from rustc_query_append

It's not actually necessary and it makes the code harder to read.

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -143,7 +143,7 @@ impl DepKind {
 }
 
 macro_rules! define_dep_nodes {
-    (<$tcx:tt>
+    (
     $(
         [$($attrs:tt)*]
         $variant:ident $(( $tuple_arg_ty:ty $(,)? ))*
@@ -179,7 +179,7 @@ macro_rules! define_dep_nodes {
     );
 }
 
-rustc_dep_node_append!([define_dep_nodes!][ <'tcx>
+rustc_dep_node_append!([define_dep_nodes!][
     // We use this for most things when incr. comp. is turned off.
     [] Null,