This removes a long-standing thing we've done, which is send a `DidSave`
notification to the language server for the clean parts of a
multi-buffer. However, it seems like the intent of that notification is
to tell the language server to reload the file from disk.
As we didn't actually write those files to disk, it seems clearer to not
send this notification; and just remove this whole code-path.
Release Notes:
- Fixed a race where autosave in a multibuffer could cause unsaved
buffers to appear saved
e4f90b5da2