Refactor the changes introduced in https://github.com/zed-industries/zed/pull/50525, in order to remove the `DisplayMap.clear_folded_buffer` method and update the editor's handling of `multi_buffer::Event::ExcerptsRemoved` to actually call `DisplayMap.unfold_buffers`, which correctly updates the `BlockMap` using its `BlockMapWriter`, ensuring that the block map is synced. Before you mark this PR as ready for review, make sure that you have: - [X] Added a solid test coverage and/or screenshots from doing manual testing - [X] Done a self-review taking into account security and performance aspects - [X] Aligned any UI changes with the [UI checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist) Release Notes: - N/A