[Extensions] Update sync unittests to use manifest v2

Update profile_signin_confirmation_helper_unittest.cc and
sync_extension_helper.cc to generate extensions with
manifest_version 2.

Bug: 816679
Change-Id: I302693e92b7925f900cd41b7fa3751a4a299a8cf
Reviewed-on: https://chromium-review.googlesource.com/1008624
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550187}
2 files changed