Remove the following warning:
```
2018-11-15 18:02:47 UpdateTip: new best=0000000000000000004626ff6e3b936941d341c5932ece4357eeccac44e6d56c height=556767 version=0x20000000 log2_work=87.722566 tx=265567564 date='2018-11-15 18:02:16' progress=1.000000 cache=18.3MiB(136657txo) warning='4 of last 100 blocks have unexpected version'
```