Fixes missing capability registration for
"workspace/didChangeWorkspaceFolders".

```
WARN  [project::lsp_store] unhandled capability registration: Registration { id: "e288546c-4458-401a-a029-bbba759d5a71", method: "workspace/didChangeWorkspaceFolders", register_options: Some(Object {}) }
```

We already correctly send back events to server on workspace add and
remove by checking this capability.
https://github.com/zed-industries/zed/blob/cf89691b85e4652093548c0bf8b79d881e26562b/crates/lsp/src/lsp.rs#L1353


https://github.com/zed-industries/zed/blob/cf89691b85e4652093548c0bf8b79d881e26562b/crates/lsp/src/lsp.rs#L1388

Release Notes:

- N/A