fix(Docs): Update docs and remove outdated reference to `MultiProvider`.
fix(Docs): Update docs and remove outdated reference to `MultiProvider`.

PiperOrigin-RevId: 204049534

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