Fix the stability attributes for std::os::fd.

As @bjorn3 pointed out [here], I used the wrong stability attribute in #98368
when making `std::os::fd` public. I set it to Rust 1.63, which was when
io-safety was stabilized, but it should be Rust 1.66, which was when
`std::os::fd` was stabilized.

[here]: rust-lang/rust#98368 (comment)

std/src/os/fd/mod.rs

@@ -3,7 +3,7 @@
 //! This module is supported on Unix platforms and WASI, which both use a
 //! similar file descriptor system for referencing OS resources.
 
-#![stable(feature = "io_safety", since = "1.63.0")]
+#![stable(feature = "os_fd", since = "1.66.0")]
 #![deny(unsafe_op_in_unsafe_fn)]
 
 // `RawFd`, `AsRawFd`, etc.
@@ -19,7 +19,7 @@ mod net;
 mod tests;
 
 // Export the types and traits for the public API.
-#[unstable(feature = "os_fd", issue = "98699")]
+#[stable(feature = "os_fd", since = "1.66.0")]
 pub use owned::*;
-#[unstable(feature = "os_fd", issue = "98699")]
+#[stable(feature = "os_fd", since = "1.66.0")]
 pub use raw::*;