fix: Remove ember-cli-deprecation-workflow

There's [an issue with ember-cli-deprecation-workflow](ember-cli/ember-cli-deprecation-workflow#133)
that causes an error during CI for the embroider optimized build.

I think we can remove `ember-cli-deprecation-workflow` from this addon
because it does not seem to be doing anything useful but maybe I'm
missing something?

This was originally added in
cibernox@c10dd8e
as part of cibernox#1431 but
there is not really much context to go off of as far as why it was
added. It seems like maybe it was added while debugging GitHub Actions
and accidentally left laying around?

- ember-cli/ember-cli-deprecation-workflow#133
- https://github.com/embroider-build/embroider/tree/main/packages/test-setup#embroideroptimizedembertryconfig