`zetacored` : remove isV2ZetaEnabled flag

```
message CrosschainFlags {
  bool isInboundEnabled = 1;
  bool isOutboundEnabled = 2;
  GasPriceIncreaseFlags gasPriceIncreaseFlags = 3;
  bool isV2ZetaEnabled = 4;
}
```
The isV2ZetaEnabled was added to allow us to easily toggle the V2ZETAFlows on and off. Once the V1 flows are deprecated and v2 becomes the default , we can remove this flag as it would be unnessary after that 