Missed some plucky configs

Author: antonblock

kokoro/config/test/ops_agent/release/plucky_aarch64.gcl

@@ -3,6 +3,8 @@ import 'common.gcl' as common
 config build = common.third_party_apps_test {
   params {
     environment {
+      platforms = []
+
       // The release builds run as a different service account.
       TRANSFERS_BUCKET = 'stackdriver-test-143416-file-transfers'
       SERVICE_EMAIL =