moblab: Update stable version to R53-8480.0.0

BUG=chromium:629981
TEST=None

Change-Id: I47d816481da0b6a9ac857ae269fe3330beb658cf
Reviewed-on: https://chromium-review.googlesource.com/362005
Commit-Ready: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
diff --git a/moblab_config.ini b/moblab_config.ini
index 925ac31..008e10b 100644
--- a/moblab_config.ini
+++ b/moblab_config.ini
@@ -17,3 +17,4 @@
 [CROS]
 # In moblab, this paramater is empty and uses the image bucket by default.
 results_storage_server:
+stable_cros_version: R53-8480.0.0