remove `beforeunload` event listener that exits VR
remove `beforeunload` event listener that exits VR

it's unneeded since Chromium builds do this automatically now (for quite some time now)
chenzlabs/aframe,aframevr/aframe,jaxmolina/ar,fernandojsg/aframe,fernandojsg/aframe,googlecreativelab/aframe,dmarcos/aframe,weddingdj/aframe,RSpace/aframe,aframevr/aframe,MatthewShotton/aframe,darkwing/aframe,wizgrav/aframe,mkungla/aframe,googlecreativelab/aframe,jaxmolina/ar,chenzlabs/aframe,RSpace/aframe,MatthewShotton/aframe,msimpson/aframe,weddingdj/aframe,mkungla/aframe,darkwing/aframe,ngokevin/aframe,msimpson/aframe,ngokevin/aframe,wizgrav/aframe,dmarcos/aframe