Rollup merge of #145200 - joshtriplett:mbe-typo-fix, r=lqd

mbe: Fix typo in attribute tracing

Author: jhpratt

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -347,7 +347,7 @@ fn expand_macro_attr(
 
     if cx.trace_macros() {
         let msg = format!(
-            "expanding `$[{name}({})] {}`",
+            "expanding `#[{name}({})] {}`",
             pprust::tts_to_string(&args),
             pprust::tts_to_string(&body),
         );