drive-by fmt cleanup

Author: estebank

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2836,7 +2836,7 @@ define_print_and_forward_display! {
 
     ty::ExistentialTraitRef<'tcx> {
         // Use a type that can't appear in defaults of type parameters.
-        let dummy_self = Ty::new_fresh(cx.tcx(),0);
+        let dummy_self = Ty::new_fresh(cx.tcx(), 0);
         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
         p!(print(trait_ref.print_only_trait_path()))
     }