doc: remove references to goma goma is not maintained anymore. Bug: angleproject:341220050 Change-Id: I0e0c9f9066498a65e77d187dfa0c6d9230de773b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5588006 Auto-Submit: Takuto Ikuta <tikuta@chromium.org> Commit-Queue: Yuly Novikov <ynovikov@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>