Revert "Run browser_tests as a 25% experiment on Mac10.13 Tests & mac_chromium_rel_ng."

This reverts commit b20ba21cddf5bd37aeaf36e4056cb019ea912635.

Reason for revert: Added capacity isn't finding bot deaths as fast as manual, targeted swarming invocations. Will reland this after having some confidence that the 10.13 bot-killer tests are identified.

Original change's description:
> Run browser_tests as a 25% experiment on Mac10.13 Tests & mac_chromium_rel_ng.
> 
> Bug: 828031
> Change-Id: I1d4bdb235ad9d93df0653215c7c5928c471b6c16
> Reviewed-on: https://chromium-review.googlesource.com/c/1277693
> Reviewed-by: Robert Sesek <rsesek@chromium.org>
> Commit-Queue: John Budorick <jbudorick@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#599364}

TBR=rsesek@chromium.org,jbudorick@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 828031
Change-Id: I38c447f53d533eeff40abfd462c3bb1f09eac75f
Reviewed-on: https://chromium-review.googlesource.com/c/1282283
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599869}
2 files changed