Update kusama/polkadot bootnodes (#1895)

closes: https://github.com/paritytech/devops/issues/2090

## Changes
1. Updated the list of bootnodes.
2. Merged the Connect node and bootnode into a single node.
3. Decreased the number of nodes.
4. Updated the DNS name.

## Description
The initial 8 bootnodes were planned to be replaced by community
bootnodes, the community node was added but we did not bother to reduce
the Parity managed bootnodes. Fixing it now.