We don't use the WebGLLoadPolicy mechanism any more. Remove all the code.
<rdar://problem/101569935>
Pull request: https://github.com/WebKit/WebKit/pull/5792
Committed 256114@main (82d2d64c2ad7): <https://commits.webkit.org/256114@main> Reviewed commits have been landed. Closing PR #5792 and removing active labels.