Delete rows in the peer_count table that are older than a week

[majecty]

We are removing rows in the network_usage table that were inserted more than a week ago to reduce the usage of disk. We use the network usage table to find strange network throughputs. Since we will check the strange network behavior when it appeared, we don't need to save the previous data.

The purpose of the peer_count table is the same as the network_usage table. We need to remove old rows in the peer_count table.