The correct define is ANGLE_HAS_RAPIDJSON

Bug: angleproject:5858
Change-Id: I21e3f3e632d5ceb4fce43f1d6be34e4fbbdafbc6
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2822254
Commit-Queue: Gert Wollny <gert.wollny@collabora.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>