(EmpowHER-303) A Phase 3, Randomized, Open-label, Multicenter, Controlled Study to Evaluate the Efficacy and Safety of Zanidatamab in Combination With Physician's Choice Chemotherapy Compared to Trastuzumab in Combination With Physician's Choice Chemotherapy for the Treatment of Participants With Metastatic HER2-positive Breast Cancer Who Have Progressed on, or Are Intolerant to, Previous Trastuzumab Deruxtecan Treatment