live_kit_server: Re-remove protocol submodule (#15317)

Marshall Bowers created 

This PR re-removes the `protocol` submodule from `live_kit_server`,
since it was incorrectly added back in #15313.

Release Notes:

- N/A

Change summary

crates/live_kit_server/protocol | 1 -
1 file changed, 1 deletion(-)

Detailed changes