Current debian build failing [1].
```
10:45:28 W: GPG error: https://downloads.apache.org/cassandra/debian 40x InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5E85B9AE0B84C041
```
This is updated out of the debian repository keys file [2].
Local tests concur it's working [3]
[1] https://jenkins.softwareheritage.org/job/debian/job/packages/job/DSTO/job/gbp-buildpackage/372/console
[2] https://downloads.apache.org/cassandra/KEYS
[3] https://forge.softwareheritage.org/P1103
Related to T3418