Revert "doc: Removed use of gendered pronouns"

@isaacs may have his commit bit but that does not mean he is at liberty
to land patches at will.  All patches have to be signed off by either
me or Bert.  Isaac, consider yourself chided.

This reverts commit 47d98b6.

src/unix/fs.c

@@ -302,7 +302,7 @@ static ssize_t uv__fs_sendfile_emul(uv_fs_t* req) {
    *
    * 1. Read errors are reported only if nsent==0, otherwise we return nsent.
    *    The user needs to know that some data has already been sent, to stop
-   *    them from sending it twice.
+   *    him from sending it twice.
    *
    * 2. Write errors are always reported. Write errors are bad because they
    *    mean data loss: we've read data but now we can't write it out.

src/unix/stream.c

@@ -679,8 +679,8 @@ static void uv__write_req_finish(uv_write_t* req) {
   /* Only free when there was no error. On error, we touch up write_queue_size
    * right before making the callback. The reason we don't do that right away
    * is that a write_queue_size > 0 is our only way to signal to the user that
-   * they should stop writing - which they should if we got an error. Something
-   * to revisit in future revisions of the libuv API.
+   * he should stop writing - which he should if we got an error. Something to
+   * revisit in future revisions of the libuv API.
    */
   if (req->error == 0) {
     if (req->bufs != req->bufsml)