Project Browser is broken on 11.x-dev because the SourceConverter service can't be loaded

Problem/Motivation

Project Browser is broken on core 11.x-dev:
You have requested a non-existent service "Drupal\project_browser\Routing\SourceConverter".

A search of core changes points to #3436295: ParamConverterManager lazy services are broken and should use a service locator as the cause. Changing SourceConverter to public fixes it, but not sure if that is the desired approach.

Steps to reproduce

1. Install Drupal CMS on 11.x-dev
2. Visit the modules page and see the error

Proposed resolution