fix(dht): Do not limit neighbor list in `PeerManager#onKBucketPing`

[teogeb]

When we sort the oldContacts, we should sort all contacts, not just a subset? In practice the oldContacts array length is already limited by the numberOfNodesPerKBucket (see PeerManager.ts:82), so there is no need to re-limit it in the PeerManager#onKBucketPing function?