Move confirmation to remove mixer channels outside MixerView::deleteChannel #7154)

Moves the confirmation to remove mixer channels outside of `MixerView::deleteChannel` and into `MixerChannelView::removeChannel`. This is so that the confirmation only applies when the user uses the context menu to remove a channel, which is important since no confirmation should apply when, for example, the mixer view is cleared with calls to `MixerView::clear`.

include/MixerChannelView.h

@@ -104,6 +104,7 @@ namespace lmms::gui
         void moveChannelRight();
 
     private:
+        bool confirmRemoval(int index);
         QString elideName(const QString& name);
         MixerChannel* mixerChannel() const;
         auto isMasterChannel() const -> bool { return m_channelIndex == 0; }

include/MixerView.h

@@ -78,7 +78,6 @@ public:
 
 	// notify the view that a mixer channel was deleted
 	void deleteChannel(int index);
-	bool confirmRemoval(int index);
 
 	// delete all unused channels
 	void deleteUnusedChannels();