[TASK] Upgrade Gerrit to 3.9.7
https://www.gerritcodereview.com/3.9.html#397
Updated plugins from https://gerrit-ci.gerritforge.com/plugin-manager/
- saml to ff160213fc
- healthcheck to v3.5.6-32-gfd330fe0fe
- avatars-gravatar to b687eb0b55
- replication-status to 469efa8c0c