[core-auth] Fix 'browser' path configuration in core-auth

[daviwil]

This corrects the browser configuration in core-auth's package.json file to ensure that it points to the correct browser output file. Presumably this would only affect consumers who are trying to directly reference this library in a Rollup build.

It actually looks like sdk/template/template may have this configured incorrectly, that's where I copied it from. @bterlson: do you know if this file remapping in browser is needed for consumers of our libraries?

[mikeharder]

I agree that template is configured incorrectly, but I'm surprised the template browser-based tests didn't fail because of this. The issue might be masked by the way we build the bundle for browser testing. I've created an issue for myself to investigate this, add tests, and fix any broken packages:

#4461

[daviwil]

Thanks Mike! I confirmed with @bterlson offline that we should have these paths set correctly even if it seems Rollup doesn't resolve them in our current builds. He suggests that we could add a linting check for it too, possibly as a result of @arpanlaha's work.

For now I'll go ahead and merge this and then I can help you with the testing story for #4461.