Hovers in Markdown vs LanguageId

[cdietrich]

Hi,

the hover provider does the following

langium/packages/langium/src/lsp/hover-provider.ts

Line 64 in 6f9c6d7

language: this.languageId,

this leads to the markdown not properly rendered

vs

[msujew]

Looking at the spec, it really seems like we're using the language field incorrectly. I'll provide a PR to remove that.

Edit: Created and merged #2067.