Miranda's character ending will now change when Nanna dies

Added the process that Miranda's character ending will now change when Nanna dies.

In the past update, Leif would confess his love to Miranda instead of Nanna if certain conditions were met, but the character ending remained unchanged. With this change, there is a possibility that Leif and Miranda will be together. If Nanna is alive, he will definitely end up with Nanna, so if you are a Miranda fan, let's plot Nanna to death. This development is based on the concept of love value in FE4.

Regardless of whether Leif confesses his love or not, this change is only based on Nanna's survival or not.