Typo in OPF formulation in README

[priyald17]

Equation (5) currently contains the term $-\mathbf{Y_i}^s|V_i|^2$.

However, I believe this should be $-(\mathbf{Y_i}^s)^*|V_i|^2$ -- that is, the shunt admittance should be conjugated.

[ccoffrin]

That's right, good catch. The software is correct but this documentation is not.