Set expiration timeout for tasks to 48 hours

We are seeing failures on the bots when they can't keep up

Bug: 124643718
Change-Id: Ic363ce94fc030268777bb8b7c76e8a73e3b4773d
diff --git a/infra/config/global/cr-buildbucket.cfg b/infra/config/global/cr-buildbucket.cfg
index 6705f0a..95100f5 100644
--- a/infra/config/global/cr-buildbucket.cfg
+++ b/infra/config/global/cr-buildbucket.cfg
@@ -73,6 +73,7 @@
       dimensions: "pool:luci.r8.ci"
       service_account: "r8-ci-builder@chops-service-accounts.iam.gserviceaccount.com"
       execution_timeout_secs: 21600  # 6h
+      expiration_secs: 172800 # 48h
       swarming_tags: "vpython:native-python-wrapper"
       build_numbers: YES
       luci_migration_host: "luci-migration.appspot.com"