gpui: Refactor PlatformKeyboardLayout (#29653)

Release Notes:

- N/A

crates/gpui/src/platform/linux/platform.rs

@@ -858,26 +858,6 @@ impl crate::Modifiers {
     }
 }
 
-pub(crate) struct LinuxKeyboardLayout {
-    id: String,
-}
-
-impl PlatformKeyboardLayout for LinuxKeyboardLayout {
-    fn id(&self) -> &str {
-        &self.id
-    }
-
-    fn name(&self) -> &str {
-        &self.id
-    }
-}
-
-impl LinuxKeyboardLayout {
-    pub(crate) fn new(id: String) -> Self {
-        Self { id }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;