rust: kernel: page: remove unnecessary helper function from doctest

Doctests in `page.rs` contained a helper function `dox` which acted
as a wrapper for using the `?` operator. However, this is not needed
because doctests are implicitly wrapped in function see [1].

Link: https://doc.rust-lang.org/rustdoc/write-documentation/documentation-tests.html#using--in-doc-tests [1]
Suggested-by: Dirk Behme <dirk.behme@de.bosch.com>
Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/rust-for-linux/459782fe-afca-4fe6-8ffb-ba7c7886de0a@de.bosch.com/
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Daniel Sedlak <daniel@sedlak.dev>
Link: https://lore.kernel.org/r/20241123095033.41240-4-daniel@sedlak.dev
[ Fixed typo in SoB. Slightly reworded commit. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: wutchzone

rust/kernel/page.rs

@@ -57,19 +57,17 @@ impl Page {
     /// ```
     /// use kernel::page::Page;
     ///
-    /// # fn dox() -> Result<(), kernel::alloc::AllocError> {
     /// let page = Page::alloc_page(GFP_KERNEL)?;
-    /// # Ok(()) }
+    /// # Ok::<(), kernel::alloc::AllocError>(())
     /// ```
     ///
     /// Allocate memory for a page and zero its contents.
     ///
     /// ```
     /// use kernel::page::Page;
     ///
-    /// # fn dox() -> Result<(), kernel::alloc::AllocError> {
     /// let page = Page::alloc_page(GFP_KERNEL | __GFP_ZERO)?;
-    /// # Ok(()) }
+    /// # Ok::<(), kernel::alloc::AllocError>(())
     /// ```
     pub fn alloc_page(flags: Flags) -> Result<Self, AllocError> {
         // SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it