Fix typo in Windows Build Instructions

In the "Get the code" section, shouldn't it be "fetch chromium"? As
it is unlikely that people who build Chromium on Windows want to target
iOS.

Also this is my first patch submission, so I think I also need to add my
name to the AUTHORS file.

BUG=

Review-Url: https://codereview.chromium.org/2545313002
Cr-Commit-Position: refs/heads/master@{#436203}
2 files changed