Remove temporary workaround for Monarch Grammar Generation

[rhazn]

We added a workaround until an issue in langium was fixed, see here:

https://github.com/jvalue/jayvee/blob/162fe0e3aeb7bb146aa4aa997b44d833e4782c2b/libs/language-server/project.json#L12

That issue is now closes as completed: https://github.com/langium/langium/issues/740 in this pull request https://github.com/langium/langium/pull/1109.

Once this is released in a new Langium version, we should remove our workaround.