[applets/mediacontroller] Don't use Album Art for icon
Summary: Icon of Media Player applet is missing in the System Tray settings when the media playing has a cover. Such icon is present when nothing is playing. Fix by not using album art in any case - icon is not longer used in tooltip, can be static. BUG: 420197 FIXED-IN: 5.19.0 Test plan: 1. play audio/video with a player compatible with Media Player applet 2. open system tray settings during playback 3. Icon of Media Player applet is always present in system tray settings, regardless of state.