perf(sound): remove blocking delay in audio device switching

Remove the 200ms blocking sleep (QThread::msleep) that was originally
used for debouncing multiple signals during device switching. Analysis
shows that valid signals arrive with sufficient intervals (>250ms),
making the blocking delay unnecessary and harmful to UI responsiveness.

移除音频设备切换中的阻塞延迟

移除原本用于防抖多个信号的 200ms 阻塞延迟（QThread::msleep）。
分析表明有效信号到达的间隔已足够大（>250ms），使得阻塞延迟既不必要
又损害 UI 响应速度。

Log: remove blocking delay in audio device switching
PMS: BUG-295929

Author: mhduiy

plugins/dde-dock/sound/soundcontroller.cpp

@@ -74,7 +74,6 @@ void SoundController::SetMute(bool in0)
 void SoundController::onDefaultSinkChanged(const QDBusObjectPath &path)
 {
     // 防止手动切换设备，与后端交互时，获取到多个信号，设备切换多次，造成混乱
-    QThread::msleep(200);
 
     if (m_defaultSinkInter)
         m_defaultSinkInter->deleteLater();