Remove misleading SafeMath comment

contracts/math/SafeMath.sol

@@ -109,7 +109,6 @@ library SafeMath {
      * - The divisor cannot be zero.
      */
     function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
-        // Solidity only automatically asserts when dividing by 0
         require(b > 0, errorMessage);
         uint256 c = a / b;
         // assert(a == b * c + a % b); // There is no case in which this doesn't hold