No need for the warning, funcion is no longer empty

TBTCSystem and DepositLog hold an independent copy of  TBTCDepositToken

TbtcSystem extedns DepositLog and theref ore the variable is shodowed.

Instead of renaming and keeping both, using only the one from
DepositLog is preferable

The return values are not used. On approvedToLog error
revert isntead of returning false.
Returning false offers the abhlity to not halt the
deposit if approvedToLog returns false.
This does not fel like a real perk. if approvedToLog returns
false the event loger is not the deposit contract, and should revert.

setTbtcDepositToken should only be called internally

…nto log-refactor