detach codebase with unsupported `allennlp` and `allennlp-models`

[davidberenstein1957]

@Masboes @rdeheer2 This is a typical example of a high prior task, which I will not be able to pick up easily. Similarly, if not done, this will break potential to update the package in the long run, due to the fact that allennlp is no longer supported.

[Masboes]

Thanks, will add it to the planning.