[skylab_tests] add sven and service account as file owner

We need to manual approve generated cl like crrev.com/c/3130887
multiple times until we can turn on autosubmit with the service account.
Also having a team member owning the files can help approve any urgent
changes for the roller in the future.

Bug: 1221644
Change-Id: I249fd660d380db0b52a2bbc506c76ca6303fc8a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3138693


Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Jieting Yang <yjt@google.com>
Cr-Commit-Position: refs/heads/main@{#917732}