Find token price throught Uniswap v2 oracle instead of having a base price for the translator deposit.

[clesaege]

See https://github.com/kleros/kleros-interaction/blob/master/contracts/standard/arbitration/LinguoToken.sol#L257 which doesn't behave like Linguo.
https://github.com/kleros/kleros-interaction/blob/master/contracts/standard/arbitration/Linguo.sol#L246

In order to keep the deposit related to the translation value, we need to use Uniswap v2 to get the price of tokens in ETH in order to determine the deposit.