cassandra: Drop fallback for extra_headers in revision.metadata
All the data has been migrated, this fallback can now be removed.
Ref. swh/infra/sysadm-environment#2564
(looks like I missed this in !1107 (merged))
Staging instance, all changes can be removed at any time
All the data has been migrated, this fallback can now be removed.
Ref. swh/infra/sysadm-environment#2564
(looks like I missed this in !1107 (merged))