compactionInterval is not used in Helm and must removed

[prometherion]

#506 introduced a bug, causing a new etcd installation to never come up with the following error:

{"level":"warn","ts":"2024-08-07T17:00:10.938Z","caller":"etcdmain/etcd.go:146","msg":"failed to start etcd","error":"error parsing CompactionRetention: time: invalid duration \" 0\""}
{"level":"fatal","ts":"2024-08-07T17:00:10.938Z","caller":"etcdmain/etcd.go:204","msg":"discovery failed","error":"error parsing CompactionRetention: time: invalid duration \" 0\"","stacktrace":"go.etcd.io/etcd/server/v3/etcdmain.startEtcdOrProxyV2\n\tgo.etcd.io/etcd/server/v3/etcdmain/etcd.go:204\ngo.etcd.io/etcd/server/v3/etcdmain.Main\n\tgo.etcd.io/etcd/server/v3/etcdmain/main.go:40\nmain.main\n\tgo.etcd.io/etcd/server/v3/main.go:32\nruntime.main\n\truntime/proc.go:225"}

The bug was introduced due to a misunderstanding in the terminology similarity.