Run stress tests on >=ToT-2 releases nightly.

Changed the suite scheduler to run stress tests on >=ToT-2. Devices
usually FSI on releases older than ToT, and we need this data for
generating relevant stress lab reports.

BUG=None
TEST=None

Change-Id: If457f114e34e513ad1f01d641bda57a8aabe826a
Reviewed-on: https://chromium-review.googlesource.com/258980
Reviewed-by: Kris Rambish <krisr@chromium.org>
Commit-Queue: Yusuf Mohsinally <mohsinally@chromium.org>
Tested-by: Yusuf Mohsinally <mohsinally@chromium.org>
diff --git a/suite_scheduler.ini b/suite_scheduler.ini
index a98e6ba..5749c6d 100644
--- a/suite_scheduler.ini
+++ b/suite_scheduler.ini
@@ -347,35 +347,35 @@
 [NightlyStress]
 run_on: nightly
 suite: stress
-branch_specs: ==tot
+branch_specs: >=tot-2
 pool: stress
 file_bugs: True
 
 [NightlyStressPool2]
 run_on: nightly
 suite: stress2
-branch_specs: ==tot
+branch_specs: >=tot-2
 pool: stress2
 file_bugs: True
 
 [NightlyStressPool3]
 run_on: nightly
 suite: stress3
-branch_specs: ==tot
+branch_specs: >=tot-2
 pool: stress3
 file_bugs: True
 
 [NightlyStressPool4]
 run_on: nightly
 suite: stress4
-branch_specs: ==tot
+branch_specs: >=tot-2
 pool: stress4
 file_bugs: True
 
 [NightlyStressPool5]
 run_on: nightly
 suite: stress5
-branch_specs: ==tot
+branch_specs: >=tot-2
 pool: stress5
 file_bugs: True