doc: Stdin is locked for reads, not writes

src/libstd/io/stdio.rs

@@ -141,8 +141,8 @@ fn handle_ebadf<T>(r: io::Result<T>, default: T) -> io::Result<T> {
 ///
 /// Each handle is a shared reference to a global buffer of input data to this
 /// process. A handle can be `lock`'d to gain full access to [`BufRead`] methods
-/// (e.g. `.lines()`). Writes to this handle are otherwise locked with respect
-/// to other writes.
+/// (e.g. `.lines()`). Reads to this handle are otherwise locked with respect
+/// to other reads.
 ///
 /// This handle implements the `Read` trait, but beware that concurrent reads
 /// of `Stdin` must be executed with care.