Use JointHidden in a couple of suitable places.

This has no notable effect, but it's appropriate because the relevant
tokens are followed by delimiters.

compiler/rustc_ast/src/tokenstream.rs

@@ -661,11 +661,11 @@ fn desugared_tts(attr_style: AttrStyle, data: Symbol, span: Span) -> Vec<TokenTr
             if attr_style == AttrStyle::Inner {
                 vec![
                     TokenTree::token_joint(token::Pound, span),
-                    TokenTree::token_alone(token::Not, span),
+                    TokenTree::token_joint_hidden(token::Not, span),
                     body,
                 ]
             } else {
-                vec![TokenTree::token_alone(token::Pound, span), body]
+                vec![TokenTree::token_joint_hidden(token::Pound, span), body]
             }
         }
     }