The ngUpgrade examples mostly rely upon SystemJS configuration.
This commit tidies up how these examples are built and tested so that
it will be easier to migrate them to work with Angular 11.2.x
PR Close#41689
There were some `systemjs.config.web[.build].js` files in the `systemjs`
boilerplate directory that are not used any more. In the past, these
files were used in the Plunker-based live examples, but we no longer use
Plunker for live examples.
This commit removes these obsolete files.
PR Close#38173
