Removing obsolete comment - explicit check in place (#851)

contracts/token/ERC20/BasicToken.sol

@@ -32,7 +32,6 @@ contract BasicToken is ERC20Basic {
     require(_to != address(0));
     require(_value <= balances[msg.sender]);
 
-    // SafeMath.sub will throw if there is not enough balance.
     balances[msg.sender] = balances[msg.sender].sub(_value);
     balances[_to] = balances[_to].add(_value);
     Transfer(msg.sender, _to, _value);