remote server: Fix language servers not starting (#19821)

PR #19653 change the code in this diff, which lead to the remote_server
binary trying to load language grammars, which in turn failed, and
stopped languages from being loaded correctly.

That then lead to language servers not starting up.

This change reintroduces what #19653 removed, so that we don't load the
grammar on the remote_server, by ignoring the grammar name from the
config. The tests still all work.


Release Notes:

- N/A

Co-authored-by: Bennet <bennet@zed.dev>