I am not sure that you are reporting the problem correctly. The maximum of the two throws is $2$ **and** there are no $6$ precisely if the maximum of the two throws is $2$. So the probability is $\dfrac{3}{36}$.
**Maybe** you were asked for the probability that the maximum of the throws is $2$ **given** that there was no $6$. Then by using the ordinary conditional probability procedure, we find that the probability the maximum is $2$ given there is no $6$ is $\dfrac{\frac{3}{36}}{\frac{25}{36}}$, which is $\dfrac{3}{25}$.