[DependencyInjection] Removed outdated FIXME comments.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

I stumbled upon two FIXME comments in the `ContainerBulderTest` which were introduced in 7796eb21. 

It looks like the intention was that parameters in the builder should be resolved without having to compile the container. Unless we agree to change the behaviour at this point (the change was introduced over 3 years ago), the comments should be removed.