Revert "Modify browser tests to wait for UploadSecurityEventReport call."

This reverts commit f699a825b3a55509394093d8057adf5086241493.

Reason for revert: Causing test SavePackageDeepScanningBrowserTest.KeepAfterWarning to be flaky.

Dashboard: https://ci.chromium.org/ui/test/chromium/ninja%3A%2F%2Fchrome%2Ftest%3Abrowser_tests%2FSavePackageDeepScanningBrowserTest.KeepAfterWarning?q=V%3Abuilder%3DLinux%2520Chromium%2520OS%2520ASan%2520LSan%2520Tests%2520%281%29+V%3Aos%3DUbuntu-22.04+V%3Atest_suite%3Dbrowser_tests

Bug: 408452167
Original change's description:
> Modify browser tests to wait for UploadSecurityEventReport call.
>
> This CL adds base::RunLoop to browser tests that failed when the
> LocalIpAddressesInEvents finch experiment was enabled for all tests,
> which modifies the upload flow to be asynchronous.
>
> Bug: 408452167
> Change-Id: I1f7036653523f6f9fb7e37eed42eee833cc56aff
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6460545
> Reviewed-by: Dominique Fauteux-Chapleau <domfc@chromium.org>
> Commit-Queue: Lina Ismail <ismaill@google.com>
> Reviewed-by: thefrog <thefrog@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1451298}

Bug: 408452167
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: Iad893ccc3a659475b2a45e78428d9bc823316e0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6491228
Owners-Override: Jiacheng Guo <gjc@google.com>
Auto-Submit: Jiacheng Guo <gjc@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1451638}