Rollup merge of #97636 - nnethercote:revert-96682, r=dtolnay

Revert #96682.

The change was "Show invisible delimiters (within comments) when pretty
printing". It's useful to show these delimiters, but is a breaking
change for some proc macros.

Fixes #97608.

r? ``@petrochenkov``

Author: Dylan-DPC

proc_macro/src/lib.rs

@@ -703,12 +703,11 @@ pub enum Delimiter {
     /// `[ ... ]`
     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     Bracket,
-    /// `/*«*/ ... /*»*/`
+    /// `Ø ... Ø`
     /// An invisible delimiter, that may, for example, appear around tokens coming from a
     /// "macro variable" `$var`. It is important to preserve operator priorities in cases like
     /// `$var * 3` where `$var` is `1 + 2`.
-    /// Invisible delimiters are not directly writable in normal Rust code except as comments.
-    /// Therefore, they might not survive a roundtrip of a token stream through a string.
+    /// Invisible delimiters might not survive roundtrip of a token stream through a string.
     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     None,
 }