Update migrating-to-v5.md
Update migrating-to-v5.md

Closes #1617

PiperOrigin-RevId: 213507021

matanlurey/angular,matanlurey/angular,angulardart/angular,angulardart/angular,chalin/angular2,chalin/angular2,angulardart/angular,matanlurey/angular,chalin/angular2