fix(#Magnification): mis-use non resoure id in resource getter when magnification capability setup

In SettingsProvider, when setup magnification capability, we might mis-use the use ACCESSIBILITY_MAGNIFICATION_MODE_FULLSCREEN as the resource id then get unpredicted fail in getContext().getResources().getInteger(). Therefore, we adjust the capability variable declaration and assigning with the correct logic.

Bug: 288038773
Test: build pass
      manually
Change-Id: I189222c2971bb7b72c629780651c10b438271cdd