This reverts commit 1b3b825c7f646f2fb34e2bceb6be33f310dfeb59.

When debugging git diffs we found that this introduced a re-ordering of
messages sent to the LSP:

* User hits "format"
* Zed adjusts spacing, and sends "spaces changed" to the LSP
* Zed sends "format" to LSP

With the async approach here, the format request can now arrive before
the space changed request.

You can reproduce this with `test_strip_whitespace_and_format_via_lsp`
under some conditions.

Release Notes:

- N/A