setns: Add a doc alias (#1088)

At first I thought this wasn't bound in rustix until I went
to search the source code to look at adding it.

Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

src/thread/setns.rs

@@ -101,6 +101,7 @@ bitflags! {
 ///  - [Linux]
 ///
 /// [Linux]: https://man7.org/linux/man-pages/man2/setns.2.html
+#[doc(alias = "setns")]
 pub fn move_into_link_name_space(
     fd: BorrowedFd<'_>,
     allowed_type: Option<LinkNameSpaceType>,
@@ -118,6 +119,7 @@ pub fn move_into_link_name_space(
 ///  - [Linux]
 ///
 /// [Linux]: https://man7.org/linux/man-pages/man2/setns.2.html
+#[doc(alias = "setns")]
 pub fn move_into_thread_name_spaces(
     fd: BorrowedFd<'_>,
     allowed_types: ThreadNameSpaceType,