Reword the question in the section header too.

This adopts the wording suggested in
rust-lang/rust#97837 (comment).

std/src/os/unix/io/mod.rs

@@ -44,14 +44,14 @@
 //! Like boxes, `OwnedFd` values conceptually own the resource they point to,
 //! and free (close) it when they are dropped.
 //!
-//! ## What about `/proc/self/mem` and similar OS features?
+//! ## `/proc/self/mem` and similar OS features
 //!
 //! Some platforms have special files, such as `/proc/self/mem`, which 
 //! provide read and write access to the process's memory. Such reads
 //! and writes happen outside the control of the Rust compiler, so they do not
 //! uphold Rust's memory safety guarantees.
 //!
-//! However, this does not mean that all APIs that might allow `/proc/self/mem`
+//! This does not mean that all APIs that might allow `/proc/self/mem`
 //! to be opened and read from or written must be `unsafe`. Rust's safety guarantees
 //! only cover what the program itself can do, and not what entities outside
 //! the program can do to it. `/proc/self/mem` is considered to be such an