JsonSerializer: Fix rapidjson define usage 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>