Add registration_config to attribution simulator error path

Previously, ["registration_config"] was omitted from the error path
due to the ScopedContext going out of scope.

Bug: 1305032
Change-Id: I7844f91e24980d5e0521768859d99a389888dc6c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3515075


Reviewed-by: Nan Lin <linnan@chromium.org>
Commit-Queue: Andrew Paseltiner <apaseltiner@chromium.org>
Cr-Commit-Position: refs/heads/main@{#979729}