rust: std_vendor: simplify { .. macro! .. } with inner attributes

It is cleaner to have a single inner attribute rather than needing
several hidden lines to wrap the macro invocations.

Thus simplify them.

Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/r/20240904204347.168520-20-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/kernel/std_vendor.rs

@@ -73,8 +73,7 @@
 /// Naive factorial implementation:
 ///
 /// ```rust
-/// # #[expect(clippy::disallowed_macros)]
-/// # {
+/// # #![expect(clippy::disallowed_macros)]
 /// fn factorial(n: u32) -> u32 {
 ///     if dbg!(n <= 1) {
 ///         dbg!(1)
@@ -84,7 +83,6 @@
 /// }
 ///
 /// dbg!(factorial(4));
-/// # }
 /// ```
 ///
 /// This prints to the kernel log:
@@ -129,11 +127,9 @@
 /// invocations. You can use a 1-tuple directly if you need one:
 ///
 /// ```
-/// # #[expect(clippy::disallowed_macros)]
-/// # {
+/// # #![expect(clippy::disallowed_macros)]
 /// assert_eq!(1, dbg!(1u32,)); // trailing comma ignored
 /// assert_eq!((1,), dbg!((1u32,))); // 1-tuple
-/// # }
 /// ```
 ///
 /// [`std::dbg`]: https://doc.rust-lang.org/std/macro.dbg.html