Remove use of current `File` for new buffers that never have `File` (#20832)
Michael Sloan
created
`create_buffer` calls `Buffer::local` which sets `file` to `None`
[here](https://github.com/zed-industries/zed/blob/f12981db32f9b936cd29e39ccc7f8a0b4e54cee1/crates/language/src/buffer.rs#L629).
So there's no point in then immediately attempting to update maps that
rely on `file` being present.
Release Notes:
- N/A