refacotor: simplify mod of keyboard

src/platform/linux.rs

@@ -716,22 +716,3 @@ pub fn get_double_click_time() -> u32 {
     }
 }
 
-pub mod keyboard {
-    use crate::common::GrabState;
-    use hbb_common::{allow_err, log, message_proto::*};
-    use rdev::{Event, EventType, Key};
-    use std::sync::mpsc;
-    use std::thread;
-
-    
-
-    pub fn _legacy_keyboard_mode(event: &Event, key_event: &KeyEvent) {
-        log::info!("{:?}", event);
-    }
-
-    pub fn _client_map_keyboard_mode(event: &Event, key_event: &KeyEvent) {
-
-    }
-
-    pub fn _translate_keyboard_mode(event: &Event, key_event: &KeyEvent) {}
-}