[autotest] Limit crosbolt_perf_nightly to only tot and tot-1 build

R42 has no more build, there is no point to run the new suite for R42 builds.

BUG=chromium:483733
TEST=None

Change-Id: I5192108bbe56a71643710673b2137878ccd36c28
Reviewed-on: https://chromium-review.googlesource.com/268917
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
Trybot-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Keith Haddow <haddowk@chromium.org>
diff --git a/suite_scheduler.ini b/suite_scheduler.ini
index 5fa0030..b1dadc5 100644
--- a/suite_scheduler.ini
+++ b/suite_scheduler.ini
@@ -738,7 +738,7 @@
 [CrosboltPerfPerbuild]
 run_on: new_build
 suite: crosbolt_perf_perbuild
-branch_specs: >=tot-2
+branch_specs: >=tot-1
 pool: performance
 file_bugs: True