Fix rustfmt error / Add comment for tab character

Author: phansch

tests/ui/crashes/ice-5835.rs

@@ -1,7 +1,8 @@
-#![rustfmt::skip]
-
+#[rustfmt::skip]
 pub struct Foo {
     /// 位	
+    ///   ^ Do not remove this tab character.
+    ///   It was required to trigger the ICE.
     pub bar: u8,
 }
 

tests/ui/crashes/ice-5835.stderr

@@ -1,20 +1,10 @@
-error[E0658]: custom inner attributes are unstable
-  --> $DIR/ice-5835.rs:1:4
-   |
-LL | #![rustfmt::skip]
-   |    ^^^^^^^^^^^^^
-   |
-   = note: see issue #54726 <https://github.com/rust-lang/rust/issues/54726> for more information
-   = help: add `#![feature(custom_inner_attributes)]` to the crate attributes to enable
-
 error: using tabs in doc comments is not recommended
-  --> $DIR/ice-5835.rs:4:10
+  --> $DIR/ice-5835.rs:3:10
    |
 LL |     /// 位    
    |           ^^^^ help: consider using four spaces per tab
    |
    = note: `-D clippy::tabs-in-doc-comments` implied by `-D warnings`
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.