updater: fix integration test CreateCorrectAndIncorrectScopeProxies

I could not repro this at all, but all the cases where the test fails in
various build, I see that the result is
`UpdateService::Result::kInvalidArgument`. So I added that condition
into the assert. The theory I have is that there is an existing
installation of the opposite scope somehow on the machine when the test
fails, and that version returns
`UpdateService::Result::kInvalidArgument`.

Fixed: 441591941
Change-Id: Ie528fe7a093b2cdb817d9bddd22f2126532d1134
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6892283
Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Auto-Submit: S Ganesh <ganesh@chromium.org>
Commit-Queue: S Ganesh <ganesh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1507485}