Add (2,1)-QRAO and fix the coefficient of (3,1)-QRAO

[Jacomichi]

Change

This PR mainly makes two corrections and one addition.
The items to be corrected are as follows.

1. Correction of the coefficients of (3,1)-QRAO. Since 3 and $\sqrt{3}$ were missing, they were added.
2. When linear or quad of IsingModel is empty, an error occurred in max when calling num_bits.

The additions are

1. (2,1)-QRAO functionality has been added.