Instance: remove redundant "virtual" keywords

src/Instance.hxx

@@ -114,14 +114,14 @@ struct Instance final
 
 private:
 #ifdef ENABLE_DATABASE
-	virtual void OnDatabaseModified() override;
-	virtual void OnDatabaseSongRemoved(const LightSong &song) override;
+	void OnDatabaseModified() override;
+	void OnDatabaseSongRemoved(const LightSong &song) override;
 #endif
 
 #ifdef ENABLE_NEIGHBOR_PLUGINS
 	/* virtual methods from class NeighborListener */
-	virtual void FoundNeighbor(const NeighborInfo &info) override;
-	virtual void LostNeighbor(const NeighborInfo &info) override;
+	void FoundNeighbor(const NeighborInfo &info) override;
+	void LostNeighbor(const NeighborInfo &info) override;
 #endif
 
 	/* callback for #idle_monitor */

src/Partition.hxx

@@ -217,11 +217,11 @@ private:
 	void OnQueueSongStarted() override;
 
 	/* virtual methods from class PlayerListener */
-	virtual void OnPlayerSync() override;
-	virtual void OnPlayerTagModified() override;
+	void OnPlayerSync() override;
+	void OnPlayerTagModified() override;
 
 	/* virtual methods from class MixerListener */
-	virtual void OnMixerVolumeChanged(Mixer &mixer, int volume) override;
+	void OnMixerVolumeChanged(Mixer &mixer, int volume) override;
 
 	/* callback for #global_events */
 	void OnGlobalEvent(unsigned mask);

src/StateFile.hxx

@@ -76,7 +76,7 @@ private:
 	bool IsModified() const;
 
 	/* virtual methods from TimeoutMonitor */
-	virtual void OnTimeout() override;
+	void OnTimeout() override;
 };
 
 #endif /* STATE_FILE_H */