Metal: Remove OS info from renderer string for WebGL contexts. This is exposing too much detailed information to the web. Replace it with the string "Unspecified Version". Bug: chromium:1354575 Change-Id: I69b8c6f7cb4eae01f806e91496664276c864309e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4574285 Commit-Queue: Kenneth Russell <kbr@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Auto-Submit: Kenneth Russell <kbr@chromium.org>