fix: update Angular deps during app migration

[DimitarTachev]

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What is the current behavior?

The Angular dependencies are not updated during tns migrate causing invalid dependencies state when migrating Angular 5 app. The invalid state is caused by the nativescript-dev-webpack plugin which updates the @angular/compiler-cli and @ngtools/webpack to 8.0.0 which are not compatible with Angular < 7.

What is the new behavior?

tns migrate is not updating the Angular deps in order to ensure compatibiltiy between@angular/compiler-cli, @ngtools/webpack and the rest of the Angular dependencies.