fix(audio): address CoreML VAD review feedback

crates/chanora_audio/src/engine.rs

@@ -312,7 +312,6 @@ pub struct AudioEngine {
     voice_activity_selector: Option<Arc<crate::TransmitModeSelector>>,
     #[cfg(any(target_os = "ios", target_os = "macos", target_os = "android"))]
     mic_gain: f32,
-    #[cfg(any(target_os = "ios", target_os = "macos"))]
     // Streams must be dropped to stop audio. Both are `!Send` because
     // cpal's Stream isn't Send on some backends; we keep them in an
     // Option wrapped by Mutex so stop() can move them out. On Linux