Follow-up of https://github.com/zed-industries/zed/pull/26574/files

After that PR, settings.json stopped giving completions when `"` was
typed as a key:

https://github.com/user-attachments/assets/5ff03863-024c-4c28-a7cd-8ef48a1695d8

This goes down to 


https://github.com/zed-industries/zed/blob/fb12863999e601c4ffc9afbded036e4f1f064369/crates/language/src/language.rs#L1736-L1748

which was empty before the PR, hence leading to lower `true` branch.
Now, when typing `"`, there's no scope according to 


https://github.com/zed-industries/zed/blob/fb12863999e601c4ffc9afbded036e4f1f064369/crates/project/src/lsp_store.rs#L4529-L4532

return result.

Removing `json-language-server` from `scope_opt_in_language_servers`
seems to preserve the `:` fix and restore the completions behavior.


Release Notes:

- N/A