[sheriff] Disable AlternateProtocolServerPropertiesTest.EmptyVector

It's flaky.

Bug: 1394488
Change-Id: Ic232ea0617ebd88e07c15513ef2d880ec92a78fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4064093


Owners-Override: Tommy Li <tommycli@chromium.org>
Reviewed-by: Thiabaud Engelbrecht <thiabaud@google.com>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1077076}