Remove old selection manager code in UI example
Remove old selection manager code in UI example

sereepap2029/playcanvas,sereepap2029/playcanvas,sereepap2029/playcanvas,aidinabedi/playcanvas-engine,playcanvas/engine,MicroWorldwide/PlayCanvas,playcanvas/engine,aidinabedi/playcanvas-engine,MicroWorldwide/PlayCanvas