Add RTS logic to Android test apk gn templates

The Android apk tests currently don't have their RTS filters because
don't use the standard "test" template. This CL adds the RTS logic to
what I believe is the one template used by our trybots that deviates
from the standard code path.

Bug: 1190328
Change-Id: I45049396fb1125a0e176cfbbf22c8cc4c242602c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2823098
Auto-Submit: Gregory Guterman <guterman@google.com>
Commit-Queue: Dirk Pranke <dpranke@google.com>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#882326}

diff --git a/testing/test.gni b/testing/test.gni
index c330f9391..e5d04a5b 100644
--- a/testing/test.gni
+++ b/testing/test.gni

@@ -8,13 +8,10 @@
 
 import("//build/config/chromeos/args.gni")
 import("//build/config/chromeos/ui_mode.gni")
+import("//build/config/rts.gni")
 import("//build_overrides/build.gni")
 
 declare_args() {
-  # For more info about RTS, please see
-  # //docs/testing/regression-test-selection.md
-  use_rts = false
-
   # Some component repos (e.g. ANGLE) import //testing but do not have "location_tags.json"
   tests_have_location_tags = true
 }