Remove FTP support from the EmbeddedTestServer.

Since FTP support is gone, this is no longer needed.

Bug: 333943
Change-Id: I7e0989c76ab42c36a2bbb420024a752c4f56d816
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3076540
Commit-Queue: Matt Menke <mmenke@chromium.org>
Reviewed-by: Asanka Herath <asanka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#911873}
NOKEYCHECK=True
GitOrigin-RevId: 790ff96a854f0682959f957d249614d9192b0ab3