Fixup: Don't define aiocb on emscripten

This resulted from a merge conflict with 01c72ee when rebasing my PR

Author: asomers

src/unix/linux_like/emscripten/mod.rs

@@ -342,24 +342,6 @@ s! {
 }
 
 s_no_extra_traits! {
-    #[cfg_attr(feature = "extra_traits", derive(Debug))]
-    pub struct aiocb {
-        pub aio_fildes: ::c_int,
-        pub aio_lio_opcode: ::c_int,
-        pub aio_reqprio: ::c_int,
-        pub aio_buf: *mut ::c_void,
-        pub aio_nbytes: ::size_t,
-        pub aio_sigevent: ::sigevent,
-        __td: *mut ::c_void,
-        __lock: [::c_int; 2],
-        __err: ::c_int,
-        __ret: ::ssize_t,
-        pub aio_offset: off_t,
-        __next: *mut ::c_void,
-        __prev: *mut ::c_void,
-        __dummy4: [::c_char; 24],
-    }
-
     pub struct dirent {
         pub d_ino: ::ino_t,
         pub d_off: ::off_t,