[Minor] Remove the warning of blocks generating too fast - v2.2.0-60 Echelon

[mawenpeng]

This version decreased block generating interval. When running anon-cli getinfo, it shows warnings that too many blocks generated than expected in last 4 hours. We may need to change the calculation mechanism to remove such warnings.

$ anon-cli getinfo
{
"version": 2020060,
"protocolversion": 180008,
"walletversion": 60000,
"balance": 0.00000000,
"blocks": 79458,
"timeoffset": 0,
"connections": 10,
"proxy": "",
"difficulty": 730150.4406224537,
"testnet": false,
"keypoololdest": 1573919873,
"keypoolsize": 101,
"paytxfee": 0.00000000,
"relayfee": 0.00001000,
"errors": "WARNING: abnormally high number of blocks generated, 100 blocks received in the last 4 hours (24 expected)"
}

Steps to reproduce:

• Run anond v2.2.0-60 Echelon and sync to the highest block.
• Run anon-cli getinfo .