Fix syntax for non-doc comments, and use crate:: instead of std::.

Author: sunfishcode

library/std/src/os/wasi/io/fd/tests.rs

@@ -1,11 +1,11 @@
-use std::mem::size_of;
-use std::os::wasi::io::RawFd;
+use crate::mem::size_of;
+use crate::os::wasi::io::RawFd;
 
 #[test]
 fn test_raw_fd_layout() {
-    /// `OwnedFd` and `BorrowedFd` use `rustc_layout_scalar_valid_range_start`
-    /// and `rustc_layout_scalar_valid_range_end`, with values that depend on
-    /// the bit width of `RawFd`. If this ever changes, those values will need
-    /// to be updated.
+    // `OwnedFd` and `BorrowedFd` use `rustc_layout_scalar_valid_range_start`
+    // and `rustc_layout_scalar_valid_range_end`, with values that depend on
+    // the bit width of `RawFd`. If this ever changes, those values will need
+    // to be updated.
     assert_eq!(size_of::<RawFd>(), 4);
 }