Bug 1565630 - Do searchfox C++/Rust indexing on ESR68. r=RyanVM

Differential Revision: https://phabricator.services.mozilla.com/D38084

--HG--
extra : moz-landing-system : lando

.cron.yml

@@ -117,6 +117,7 @@ jobs:
           - mozilla-central
           - mozilla-beta
           - mozilla-release
+          - mozilla-esr68
       when:
           - {hour: 10, minute: 0}